Among all the temporal activities that can be sanctified, daily work holds a primordial place in St. Josemaría's teaching. He constantly stressed that the sanctification of work “is, as it were, the hinge of true spirituality for people who, like us, have decided to come close to God while being at the same time fully involved in temporal affairs." 
And he insisted: “the sole objective of Opus Dei has always been to see to it that there be men and women of all races and social conditions who endeavour to love and to serve God and the rest of mankind in and through their ordinary work, in the midst of the realities and interests of the world." 
This teaching of St. Josemaría is a particular characteristic of the spirit God revealed to him on October 2nd, 1928. It is not the only way to approach the sanctification of temporal affairs, but it is the one that is proper and specific to the spirit of Opus Dei. Since the human condition, our human lot, is to work, “the supernatural vocation to holiness and apostolate according to the spirit of Opus Dei confirms this human vocation to work . . . one of the essential signs of this vocation is precisely a determination to remain in the world and to do a job as perfectly as possible (taking into account, of course, one's personal imperfections), both from the human and from the supernatural point of view." 
“Our ordinary activities are not an insignificant matter. Rather they are the very hinge on which our sanctity turns, and they offer us constant opportunities of meeting God, and of praising him and glorifying him through our intellectual or manual work."  In this passage and on many other occasions St. Josemaria, employing the expression the “hinge on which our sanctity turns," refers at times to work and at other times to the sanctification of work. To work, because it is the very material the hinge is made of. And to the sanctification of work, because work alone is not enough: if it is not sanctified it cannot act as a hinge in the search for holiness.
The work St. Josemaria envisages as the hinge of the spiritual life is not just any kind of activity. It does not involve tasks carried out as a “hobby" to cultivate an interest, or for other reasons, even if done out of necessity and requiring effort. It is specifically a question of professional work : the publicly recognised task— munus publicum —which each one carries out in civil society, as an activity that configures, serves and builds up society. This activity brings with it duties and responsibilities, as well as rights, including the right to a just remuneration. Professional work includes, for example, that of an architect, carpenter, teacher, or work in the home.
“Our ordinary activities are not an insignificant matter. Rather they are the very hinge on which our sanctity turns, and they offer us constant opportunities of meeting God, and of praising him and glorifying him through our intellectual or manual work."
In a certain way the priestly ministry can also be referred to as professional work (St. Josemaria does so at times  ), insofar as it is a public task at the service of all souls and, specifically, of the sanctification of the ordinary faithful in the fulfilment of their professional work, whereby they contribute to building up society in a Christian way. This mission requires the cooperation of the common and the ministerial priesthood. Although the priesthood is in itself a sacred ministry, a holy rather than a profane task, that doesn't automatically make holy the person who carries it out. The priest has to struggle to sanctify himself in the exercise of his ministry, and consequently he too can sanctify his work as the Founder of Opus Dei taught, carrying it out with a “truly priestly soul and a fully lay mentality." 
It is also worth mentioning that at times St. Josemaria used the expression “professional work" to describe illness, and also old age and other situations in life that absorb the energies one would otherwise dedicate to a profession if one were able to do so. Such would be the case for example of a person searching for a position of employment. In referring to these situations as “professional work," he makes it clear that those who find themselves in these circumstances ought to respond as if it were a professional task that has to be sanctified. Just as love for God leads us to carry out our professional duties as perfectly as possible, so also a sick person can, for love of God and with an apostolic intention, accept the demands of medical treatment, exercise or diet, and be a “good patient," obeying to the point of becoming identified with Christ, obedient unto death, even death on a cross. Thus “illness and old age, when they come, are transformed into professional work. And so the search for holiness, in accord with the spirit of the Work, is not interrupted, which, like a door on its hinge, is supported by professional work." 
Normally, though, the term “professional work" is used to describe a civil profession, and not these other situations to which it is applied by analogy. This professional work, in its proper and principal sense, is what constitutes the hinge or pivot of sanctification in the spirit of Opus Dei.
The tapestry of ordinary life
Family, professional and social duties form, as it were, a “tapestry" that is the raw material of sanctification and the apostolic terrain proper to the ordinary faithful. This tapestry can be woven in many different ways. One of the principal characteristics of the teaching of St. Josemaría is that family and social tasks are centered around professional work, a fundamental factor used by society to classify its citizens. 
Sanctification in the middle of the world demands the sanctification of the world “from the very heart of civil society, so as to fulfil St. Paul's dictum: instaurare omnia in Christo —to restore all things in Christ."  Carrying out this mission requires sanctifying the family, “the beginning and foundation of human society" and “its primary and vital cell."  But society is not simply a conjunction of families, just as a body is not a conglomerate of cells.
The social body has an organisation and structure, a life of its own. To imbue society with a Christian spirit, besides sanctifying the family, we need to sanctify social relations, creating a climate of friendship and service, giving a Christian tone to lifestyles, fashions and entertainment. Nevertheless, the diverse professional activities are what radically shape society, its organisation and life, and deeply influence family and social relations.
The sanctification of professional work (together with the sanctification of family and social life) is not only essential in order to shape society in accord with God's will, but it forms the “hinge" in the tapestry that these three aspects make up. It is not that professional duties are more important than family and social tasks, but rather that they serve as a support for the family and for social cohesion. The importance or priority of a duty depends on the order of charity, not on whether it is a professional, social or family duty.
Work can be the hinge of the whole spiritual life because, in addition to being of service for the good of the family and for the Christian configuration of society, it is also a field for attaining perfection through the exercise of virtue in ways specific to the professional setting, including justice in labor relations, responsibility and industriousness in one's work, and many expressions of fortitude, constancy, loyalty, and patience, to mention just some examples.
It is to the conjunction of all these elements that St. Josemaria is referring when he invites us to consider that “work is the vehicle through which each person is inserted into society, the means by which we find a place in the ensemble of human relationships, the instrument for assigning us a position, a place in human society. Professional work and being in the world are two sides of the same coin, two realities that mutually require one another, so that it is impossible to understand one outside the other." 
Since work is the hinge of the spiritual life in Opus Dei, we can understand why “our professional vocation is not simply a part, but rather a principal part of our supernatural vocation." 
Each one's “professional vocation" stems from a number of factors: the qualities and aptitudes we receive from God; the particular duties we have to fulfil; the needs of our family and society; the real possibilities of choosing a particular career. All these factors, and not only our preferences and likes, are what configures each one's “professional vocation." It is called a “vocation" because this conjunction of factors represents a call from God to choose the professional activity that is most appropriate as material for our sanctification and apostolate.
We should never forget, St Josemaría writes, that the professional vocation is part of our divine vocation “in so far as it is a means for attaining sanctity and for helping others to do so."  And therefore “if at any point the professional vocation were to become an obstacle . . . if it absorbs one to such an extent that it impedes interior life or the faithful fulfilment of one's duties of state . . . it is not part of the divine vocation, because it is no longer a professional vocation." 
Since our professional vocation is determined in part by our specific situation, it is not a calling to exercise a fixed and predetermined professional work independent of circumstances. “The professional vocation is something continually being defined throughout our life. It often happens that a person who began a particular course of studies discovers afterwards that he is better gifted for other jobs, and switches career; or he ends up specialising in a different field from the one foreseen at the beginning; or he finds, in the full exercise of his chosen profession, a new field of work that allows him to improve his family's social position, or to contribute more effectively to the good of the community; or he is obliged, for reasons of health, to change his environment and occupation." 
The professional vocation is a call to carry out a particular function in society: not just any one but, within the range of options available, the one best suited to the pursuit of holiness and apostolate through one's work. By carrying out this profession, one “earns a living, supports one's family, contributes to the common good, and develops one's own personality."  We shouldn't take just the easy option, as if all possibilities were equally valid, nor decide superficially, guided only by ours own preferences or career. The criterion for choosing has to be love for God and souls: the service we can offer to spread more effectively the Kingdom of Christ and further human progress, making a return on the talents we have received.
When the hinge is firmly in place the door turns safely and smoothly. When work is firmly grounded on divine filiation, when it is the work of a son or daughter of God—the “work of God," like Christ's work—the entire tapestry of ordinary life is opened to God's grace. But if the hinge is missing, how can we imbue society with a Christian spirit? If it is rusted, or bent, or badly aligned, what use will it be no matter how precious the metal it is made of?
If it conflicts with family and social duties, even to the extent of paralysing them, we would have to ask: of what value is the hinge without the door? Above all, if work is torn away from its foundation, which is divine filiation, if it is not sanctified, what meaning can it have for a Christian?
“Let us ask our Lord Jesus for light, and beg him to help us discover, at every moment, the divine meaning which transforms our professional work into the hinge on which our calling to sanctity rests and turns. In the Gospel you will find that Jesus was known as faber, filius Mariae —the workman, the son of Mary. Well, we too, with a holy pride, have to prove with deeds that we are workers, men and women who really work!" 
 St. Josemaria, Friends of God , no. 61.
 St. Josemaria, Conversations , no. 10.
 Ibid ., no. 70.
 Friends of God , no. 81.
 Cf. Friends of God , no. 265.
 St. Josemaria, Letter ,28 March 1945, no. 3.
 Phil 2:8
 St. Josemaria, notes taken from his preaching, cited by Ernst Burkhart and Javier Lopez, Vida Cotidiana y santidad en la enseñanza de san Josemaría, Madrid 2013, vol. III, p. 165.
 Cf. Vida Cotidiana y santidad en la enseñanza de san Josemaría, Madrid 2013, vol. III, pp. 222 ff.
 St. Josemaria, Letter 14 February 1950, no. 20, cited by Ernst Burkhart and Javier Lopez, Vida Cotidiana y santidad en la enseñanza de san Josemaría, Madrid 2013, vol. 1, p. 81. Quote from St. Paul is Eph 1:10.
 Second Vatican Council, Decree on the Lay Apostolate Apostolicam actuositatem , 11.
 St. Josemaria, Letter, 6 May 1945, no. 13, cited by Ernst Burkhart and Javier Lopez, Vida Cotidiana y santidad en la enseñanza de san Josemaría, Madrid 2013, vol. III, p. 161.
 St. Josemaria, Text from 31 May 1954. cited by Jose Luis Illanes in La sanctificacion del trabajo , Palabra, Madrid 1981, p. 42
 St. Josemaria, Letter, 15 October 1948, no. 7, cited by Ernst Burkhart and Javier Lopez, Vida Cotidiana y santidad en la enseñanza de san Josemaría, Madrid 2013, vol. III, p. 180.
 Ibid .
 Ibid ., no. 33.
 Conversations , no. 70
 Friends of God , no. 62 (Gospel quote is Mk 6:3)