After Jesus ascended to heaven, the witnesses of that marvelous event returned to Jerusalem from the mount called Olivet, which is near Jerusalem, a Sabbath day's journey away; and when they had entered, they went up to the upper room, where they were staying, Peter and John and James and Andrew, Philip and Thomas, Bartholomew and Matthew, James the son of Alphaeus and Simon the Zealot and Judas the son of James (Acts 1:12-14).
They were fulfilling Jesus' command to wait in the Holy City for the sending of the promised Consoler. There they waited for ten days, united around Mary.
How humanly logical we find what Holy Scripture tells us! Upon losing the physical company of their Master, the closest of his followers gathered around his Mother, who reminded them so much of Jesus: in her features, in the tone of her voice, in her affectionate and maternal glance, in the refinement of her heart, and above all in the peace she spread around her. Along with the apostles and the holy women, we also find there our Lord's closest relatives, the same ones who earlier had doubted him, and now, after converting, gathered closely around the Virgin of Nazareth.
It is easy to imagine life in that Cenacle, which must have been quite large to hold so many people. Tradition doesn't tell us to whom that house belonged, although it seems likely that is was either the house of the mother of Mark, the future evangelist, whom the Sacred Text refers to further on (see Acts 12:12), or possibly a house that the family of John the Evangelist had in the Holy City. In any case, the united prayer of the disciples with Mary quickly produced a first result: the choice of Matthias to take the place of Judas Iscariot. Once the number of the twelve apostles was complete again, they continued praying while awaiting the outpouring of the Holy Spirit that Jesus had promised them.
But they couldn't spend their whole time praying. They would have had to look after many other tasks, although, in the end, everything they did was really prayer, because their thoughts were continuously on Jesus and they had Mary with them. We can imagine their conversations—real family get-togethers—with our Lady. Now that they had seen the Risen Christ and contemplated his ascension to heaven, they wanted to know many details of their Master's life, including his infancy. And his Mother was there to evoke for them the memories that were always alive in her heart: the annunciation by Gabriel in those now distant years in Nazareth; the espousal with Joseph, whom many of them had never met; the birth in Bethlehem; the adoration of the shepherds and the Magi; the flight into Egypt; the years of hard work in the workshop at Nazareth.… How many topics Mary's words offered for the disciples' prayer! They saw with a new light all the events they had lived alongside the Master, during the three years spent accompanying him throughout the land of Palestine. Alongside Mary, the ever-faithful Virgin, their faith, hope and love were enkindled: the best preparation to receive the Paraclete.
Everything they did was really prayer, because their thoughts were continuously on Jesus and they had Mary with them.
And finally, on the day of Pentecost, suddenly a sound came from heaven like the rush of a mighty wind, and it filled all the house where they were sitting. And there appeared to them tongues as of fire, distributed and resting on each one of them. And they were all filled with the Holy Spirit (Acts 2:2-4).
News of the marvelous event reached the multitude of people present in Jerusalem: Parthians and Medes and Elamites and residents of Mesopotamia, Judea and Cappadocia, Pontus and Asia, Phrygia and Pamphylia (Acts 2:9 ff). Peter, enkindled with the power of the Holy Spirit, addressed the crowds. Afterwards the apostles dispersed throughout Galilee, Samaria and to the furthest corners of the world, carrying everywhere the good news of the Kingdom of God.
Mary gave thanks to God for those first fruits of the apostolic preaching, and for the countless faithful who would come to the Church over the centuries. All found a place in her heart of a mother, which God had given her at the moment of the incarnation of the Word and which Christ had confirmed from the wood of the Cross, in the person of the beloved disciple.