1. Jesus teaches us to turn to God as our Father
With the Our Father, Jesus Christ teaches us to turn to God as our Father: “To pray to the Father is to enter into his mystery as he is and as the Son has revealed him to us. 'The expression God the Father had never been revealed to anyone. When Moses himself asked God who he was, he heard another name. The Father's name has been revealed to us in the Son, for the name Son implies the new name Father ' (Tertullian, De oratione , 3)" (Catechism 2779).
In teaching the Our Father, Jesus reveals to his disciples that they too have been made sharers in his condition as Son. “Through the revelation of this prayer, the disciples discover a special participation for them in divine filiation, which St John was to speak of in the Prologue of his Gospel: 'To all who received him, who believed in his name, he gave power to become children of God' (Jn 1:2). So quite rightly, they pray according to his teaching, Our Father ." 
Jesus Christ always distinguishes between “my Father" and “your Father" (cf. Jn 20:17). In fact, when he prays he never says “our Father." This shows that his relationship with God is quite special; it is his own relationship and no one else's. With the Our Father prayer, Jesus wants to make his disciples aware of their condition as sons of God, indicating at the same time the difference between his natural filiation and our divine filiation by adoption, received as a gratuitous gift from God.
The Christian's prayer is that of a son of God who turns to his Father God with filial trust, which “is expressed in the liturgies of East and of West by the beautiful, characteristically Christian expression: parrhesia , straightforward simplicity, filial trust, joyous assurance, humble boldness, the certainty of being loved (cf. Eph 3:12; Heb 3:6; 4:16; 10:19; 1 Jn 2:28; 3:21; 5:14)" (Catechism 2778). The word parrhesia , which originally designated a Greek citizen's privilege of freedom of speech in popular assemblies, was adopted by the Fathers of the Church to express the filial behavior of Christians before their Father God.
2. Divine filiation and Christian fraternity
By calling God our Father, we recognize that divine filiation unites us to Christ, the firstborn among many brethren (Rom 3:29), through a real supernatural fraternity. The Church is this new communion of God and men (cf. Catechism 2790).
This is why Christian holiness, although personal and individual, is never individualist or self-centered. “if we pray the Our Father sincerely, we leave individualism behind, because the love that we receive frees us from it. The 'our' at the beginning of the Lord's Prayer, like the 'us' of the last four petitions, excludes no one. If we are to say it truthfully (cf. Mt 5:23-24; 6:14-16), our divisions and oppositions have to be overcome" (Catechism 2792).
The fraternity that divine filiation institutes extends to all men and women, because in a certain sense all are God's children—they are his creatures—and are called to be holy: “There is only one race in the world: the race of the children of God."  Therefore Christians need to be aware of their responsibility to bring all mankind to God.
Divine filiation spurs us to do apostolate, which is a necessary manifestation of filiation and of fraternity: “Be mindful of what others are—and first of all those who are at your side: children of God, with all the dignity that marvellous title entails. We have to behave as God's children toward all God's sons and daughters. Our love has to be a dedicated love, practiced every day and made up of a thousand little details of understanding, hidden sacrifice and unnoticed self-giving." 
3. Awareness of our divine filiation: foundation of the spiritual life
When one's divine filiation is lived intensely it becomes “a profound attitude of the soul which eventually permeates one's entire existence. It is there in every thought, every desire, every affection."  It is a reality to be lived constantly, not just in certain situations: “We are children of God all day long, even though we do set aside special moments for considering it, so that we can fill ourselves with the awareness of our divine filiation, the heart of true piety." 
St Josemaria teaches that the “sense" or vivid awareness of one's divine filiation “is the basis of the spirit of Opus Dei. All men are children of God. But a child can look upon his father in many ways. We must try to be children who realize that the Lord, by loving us as his children, has taken us into his house, in the middle of the world, to be members of his family, so that what is his is ours, and what is ours is his, and to develop that familiarity and confidence which prompts us to ask him, like children, for the moon!" 
Christian cheerfulness is anchored in the sense of our divine filiation: “Cheerfulness is a necessary consequence of our divine filiation, of knowing that our Father God loves us with a love of predilection, that he welcomes us, helps us and forgives us."  St Josemaria's homilies often reflect this reality in his life: “For reasons that I need not go into now (but which Jesus, who is presiding over us here from the Tabernacle, knows full well) my life has led me to realise in a special way that I am a son of God and I have experienced the joy of getting inside the heart of my Father, to rectify, to purify myself, to serve him, to understand others and find excuses for them, on the strength of his love and my own lowliness … Over the years, I have sought to rely unfalteringly for my support on this joyous reality." 
One of the most challenging questions one encounters when meditating on divine filiation is the problem of evil. Many people are unable to reconcile the experience of evil in the world with the certitude of faith in God's infinite goodness. However, the saints teach us that everything that happens in our life works for our good, because they have attained a deep understanding of the connection between divine filiation and the Holy Cross. For example, when St Thomas More was incarcerated in the Tower of London, he told his eldest daughter: “My dear daughter, never let your soul be upset by whatever happens to me in this life. Nothing can happen unless God wants it. And I am quite sure that, come what may, however bad it may seem, it will be for the good."  St Josemaria teaches the same thing in relation to situations that are less dramatic, but where a Christian soul may lose its peace: “Woes? Setbacks deriving from one thing or another? Can't you see that this is the will of your Father—God... He is good... and He loves you—loves you personally—more than all the mothers in the world can possibly love their children?" 
For St Josemaria, divine filiation is not a sugary reality, far removed from any suffering and pain. On the contrary, he sees it as a reality intrinsically linked to the Cross, which is necessarily present in all those who want to follow Christ closely: “Jesus prays in the garden. Pater mi (Mt 26:39), Abba Pater! (Mk 14:36). God is my Father, even though he may send me suffering. He loves me tenderly, even while wounding me. Jesus suffers, to fulfil the Will of the Father... And I, who also wish to fulfil the most holy Will of God, following in the footsteps of the Master, can I complain if I too meet suffering as my travelling companion? It will be a sure sign of my sonship, because God is treating me as he treated his own Divine Son. Then I, just as He did, will be able to groan and weep alone in my Gethsemani; but, as I lie prostrate on the ground, acknowledging my nothingness, there will rise up to the Lord a cry from the depths of my soul: Pater mi, Abba, Pater... fiat! " 
Another important consequence of the awareness of our divine filiation is filial abandonment into God's hands. This is not so much the result of personal ascetical struggle, though that is a necessary condition, but of letting oneself be led by God, whence the need for “abandonment." It involves an active abandonment, a free and conscious abandonment on the part of a son or daughter. This attitude has given rise to a specific way of living divine filiation (which is not the only way, or obligatory for everyone) called “spiritual childhood." This path consists in seeing oneself not only as a child, but as a small, needy child before God. St Francis of Sales described it as follows: “ If you do not become as simple as children you will not enter into the kingdom of my Father (cf. Mt 18:3). As long as a child is small it remains very simple; it knows only its mother; it has only one love, its mother; it has only one desire, the lap of its mother; it wants only to recline in such lovable peace. The perfectly simple soul has only one love, God; and in this single love, a single desire, to rest in the bosom of the heavenly Father and there to find its repose, like a loving son leaving everything completely to his Father's care, seeking nothing but to remain is this holy confidence."  St Josemaria also recommended taking the path of spiritual childhood: “Being children you will have no cares: children quickly forget what troubles them and return to their games. With abandonment, therefore, you will not have to worry, since you will rest in the Father." 
4. The seven petitions of the Our Father
In the Lord's prayer, the first invocation, Our Father who art in heaven , is followed by seven petitions. “the object of the first three petitions is the glory of the Father: the sanctification of his name, the coming of the kingdom, and the fulfillment of his will. The four others present our wants to him: they ask that our lives be nourished, healed of sin, and made victorious in the struggle of good over evil" ( Catechism 2857).
The Our Father is the model for all prayer, as St Thomas Aquinas teaches: “The Lord's prayer is the most perfect of prayers … In it we not only ask for all the things we can rightly desire, but also in the sequence that we ought to desire them. Thus this prayer not only teaches us to ask for things, but also in what order we ought to desire them." 
First petition: “Hallowed be thy name"
No creature can increase God's holiness. Therefore “the term 'to hallow' is to be understood here not primarily in its causative sense (only God hallows, makes holy), but above all in an evaluative sense: to recognize as holy, to treat in a holy way … Beginning with this first petition to our Father, we are immersed in the innermost mystery of his Godhead and the drama of the salvation of our humanity. Asking the Father that his name be made holy draws us into his plan of loving kindness for the fullness of time, 'according to his purpose which he set forth in Christ,' that we might 'be holy and blameless before him in love' (cf. Eph 1, 9 and 4)" (Catechism 2807). Thus the first petition asks that God's holiness may shine forth and increase in our lives: “Who could sanctify God since it is he who sanctifies? Inspired by the words 'You shall be holy to me for I the Lord am holy' ( Lev 20,26), we ask, sanctified by baptism, that we may persevere in what we have begun to be. And we ask for it every day because every day we fall and need to purify our sins through continual sanctification… And so we turn to prayer that this sanctity may remain in us."  Second petition: “Thy kingdom come"
The second petition expresses the hope that the time will come when God will be recognized by everyone as their King, who will shower his gifts on us: “This petition is Marana tha , the cry of the Spirit and the Bride: 'Come, Lord Jesus' ( Rev 22:20) … In the Lord's Prayer, 'thy kingdom come' refers primarily to the final coming of the reign of God through Christ's return (cf. Tit 2:13)" ( Catechism 2817-2818). Furthermore, God's kingdom was inaugurated in this world with the coming of Christ and the sending of the Holy Spirit: “'The kingdom of God [is] righteousness and peace and joy in the Holy Spirit'( Rom 14:17). The end-time in which we live is the age of the outpouring of the Spirit. Ever since Pentecost, a decisive battle has been joined between 'the flesh' and the Spirit (cf. Gal 5, 16-25). 'Only a pure soul can boldly say: Thy kingdom come . One who has heard Paul say, Let not sin therefore reign in your mortal bodies (cf. Rom 6:5), and has purified himself in action, thought and word will say to God: Thy kingdom come! ' (St Cyril of Jerusalem, Catecheses mystagogicæ , 5, 13)" ( Catechism 2819). Thus in the second petition we express our desire that God may reign in us now through grace, that his Kingdom on earth may each day be more extensive, and that at the end of time he may reign fully over all in Heaven.
Third petition: “Thy will be done on earth as it is in heaven"
God's will is that all men be saved and come to the knowledge of the truth (cf. 1 Tim 2:3-4). Jesus teaches us that the one who does the will of my Father who is in heaven enters the kingdom of heaven (cf. Mt 7:21). Therefore, here “we ask our Father to unite our will to his Son's, in order to fulfill his will, his plan of salvation for the life of the world. We are radically incapable of this, but united with Jesus and with the power of his Holy Spirit, we can surrender our will to him and decide to choose what his Son has always chosen: to do what is pleasing to the Father (cf. Jn 8:29)" (Catechism 2825). As a Father of the Church says, when we pray in the Our Father thy will be done on earth as it is in heaven , we ask this “not in the sense that God should do what he wants but rather that we may be able to do what God wants."  Moreover, the expression on earth as it is in heaven contains the petition that here on earth we may long to accomplish God's will as it has been accomplished by the angels and the blessed in heaven.
Fourth petition: “Give us this day our daily bread"
This petition expresses the filial abandonment of God's children, since “the Father who gives us life cannot but give us the nourishment life requires—all appropriate goods and blessings, both material and spiritual" (Catechism 2830). Christians understand that this fourth petition “concerns the Bread of Life: the Word of God accepted in faith, the Body of Christ received in the Eucharist (cf. Jn 6:26-28)" ( Catechism 2835). Regarding the term daily : “Taken in a temporal sense, this word is a pedagogical repetition of 'this day,' (cf. Ex 16:19-21) to confirm us in trust 'without reservation.' Taken in the qualitative sense, it signifies what is necessary for life, and more broadly every good thing sufficient for subsistence (cf. 1 Tim 6:8)." (Catechism 2837)
Fifth petition: “Forgive us our trespasses as we forgive those who trespass against us"
In this petition we begin by acknowledging our condition as sinners: “we return to him like the prodigal son (cf. Lk 15:11-32) and, like the tax collector (cf. Lk 18:13), recognize that we are sinners before him. Our petition begins with a 'confession' of our wretchedness and his mercy" (Catechism 2839). But this petition will not be heard if we have not satisfied the requirement of forgiving those who have offended us: “this outpouring of mercy cannot penetrate our hearts as long as we have not forgiven those who have trespassed against us. Love, like the Body of Christ, is indivisible; we cannot love the God we cannot see if we do not love the brother or sister we do see (cf. 1 Jn 4:20). In refusing to forgive our brothers and sisters, our hearts are closed and their hardness makes them impervious to the Father's merciful love" (Catechism 2840).
Sixth petition: “Lead us not into temptation"
This petition is related to the preceding one because sin is the consequence of consenting freely to temptation. That is why we now “ask our Father not to 'lead' us into temptation … We ask him not to allow us to take the way that leads to sin. We are engaged in the battle 'between flesh and spirit'; this petition implores the Spirit of discernment and strength" ( Catechism 2846). God always gives us grace to overcome temptation: God is faithful, and he will not let you be tempted beyond your strength, but with the temptation will also provide the way of escape, that you may be able to endure it (1 Cor 10:13). But to overcome all temptation we need to pray: “Such a battle and such a victory become possible only through prayer. It is by his prayer that Jesus vanquishes the tempter, both at the outset of his public mission (cf. Mt 4:11) and in the ultimate struggle of his agony (cf. Mt 26:36-44). In this petition to our heavenly Father, Christ unites us to his battle and his agony … this petition takes on all its dramatic meaning in relation to the last temptation of our earthly battle; it asks for final perseverance . 'Lo, I am coming like a thief! Blessed is he who is awake' ( Rev 16:15)" (Catechism 2849).
Seventh petition: “But deliver us from evil"
The last petition is found in Jesus' priestly prayer to his Father: I do not pray that thou shouldst take them out of the world, but that thou shouldst keep them from the evil one ( Jn 17:15) In this petition “evil is not an abstraction, but refers to a person, Satan, the Evil One, the angel who opposes God. The devil ( dia-bolos ) is the one who 'throws himself across' God's plan and his work of salvation accomplished in Christ" ( Catechism 2851). Moreover, “When we ask to be delivered from the Evil One, we pray as well to be freed from all evils, present, past, and future, of which he is the author or instigator" ( Catechism 2854), and especially from sin, the one true evil,  and its punishment: eternal condemnation. Other evils and tribulations can be turned into benefits if we accept them and unite them to Christ's suffering on the Cross.
Catechism of the Catholic Church , 2759-2865.
Benedict XVI/Joseph Ratzinger, Jesus of Nazareth , ch. 5.
St Josemaria, “Getting to Know God" and “Towards Holiness" in Friends of God , 142-153 and 294-316.
Bonaventure PERQUIN, Abba Father , Scepter 2002.
 John Paul II, Address , 1 July 1987, 3.
 St Josemaria, Christ is Passing by , 13.
 Ibid. , 36.
 St Josemaria, Friends of God , 146.
 St Josemaria, Conversations , 102.
 St Josemaria, Christ is Passing by , 64.
 St Josemaria, The Forge , 332
 St Josemaria, Friends of God , 143.
 St Thomas More, Letters from the Tower , no. 7.
 St Josemaria, The Forge , 929.
 St Josemaria, The Way of the Cross , 1st Station, Points for Meditation, 1.
 St Francis of Sales, Spiritual Conversations , no. 16, 7.
 St Josemaria, The Way , 864.
 St Thomas Aquinas, Summa theologiæ , II-II, q. 83, a. 9.
 St Cyprian, De dominica oratione , 12.
 Ibid ., 14.
 Cf. The Way , 386.