From: Luke 2:41-51
The Finding in the Temple
41] Now his (Jesus') parents went to Jerusalem every year at the feast of the Passover.  And when he was twelve years old, they went up according to custom;  and when the feast was ended, as they were returning, the boy Jesus stayed behind in Jerusalem. His parents did not know it, [44 but supposing him to be in the company they went a day's journey, and they sought him among their kinsfolk and acquaintances;  and when they did not find him, they returned to Jerusalem, seeking him.  And after three days they found him in the temple sitting among the teachers, listening to them and asking them questions;  and all who heard him were amazed at his understanding and his answers.  And when they saw him they were astonished; and his mother said to him, "Son, why have you treated us so? Behold, your father and I have been looking for you anxiously."  And he said to them, "How is it that you sought me? Did you not know that I must be in my Father's house?"  And they did not understand the saying which he spoke to them.
The Hidden Life of Jesus at Nazareth
 And he went down with them and came to Nazareth, and was obedient to them; and his mother kept all these things in her heart.
41. Only St Luke (2:41-50) reports the event of the Child Jesus being lost and then found in the temple, which we contemplate in the "Fifth Joyful Mystery" of the Rosary.
Only males aged twelve and upwards were required to make this journey. Nazareth is about 100 km (60 miles) from Jerusalem as the crow flies, but the hilly nature of the country would have made it a trip of 140 km.
43-44. On pilgrimages to Jerusalem, the Jews used to go in two groups--one of men, the other of women. Children could go with either group. This explains how they could go a day's journey before they discovered the Child was missing when the families regrouped to camp.
"Mary is crying. In vain you and I have run from group to group, from caravan to caravan. No one has seen him. Joseph, after fruitless attempts to keep from crying, cries too.... And you.... And I.
'Being a common little fellow, I cry my eyes out and wail to heaven and earth..., to make up for the times when I lost him through my own fault and did not cry" ([St] J. Escriva, "Holy Rosary", Fifth Joyful Mystery).
45. The concern which Mary and Joseph show in looking for the Child should encourage us always to seek Jesus out, particularly if we lose him through sin.
"Jesus, may I never lose you again.... Now you and I are united in misfortune and grief, as were united in sin. And from the depths of our being comes sighs of heartfelt sorrow and burning phrases which the pen cannot and should not record" ("Holy Rosary", Fifth Joyful Mystery).
46-47. The Child Jesus must have been in the courtyard of the temple, which was where the teachers usually taught. Listeners used to sit at their feet, now and again asking questions and responding to them. This was what Jesus did, but his questions and answers attracted the teachers' attention, he was so wise and well-informed.
48. Ever since the Annunciation our Lady had known that the Child Jesus was God. This faith was the basis of her generous fidelity throughout her life--but there was no reason why it should include detailed knowledge of all the sacrifices God would ask of her, nor of how Christ would go about his mission of redemption: that was something she would discover as time went by, contemplating her Son's life.
49. Christ's reply is a form of explanation. His words--his first words to be recorded in the Gospel--clearly show his down Sonship; and they also show his determination to fulfill the will of his Eternal Father. "He does not upbraid them--Mary and Joseph--for searching for their son, but he raises the eyes of their souls to appreciate what he owes him whose Eternal Son he is" (St Bede, "In Lucae Evangelium Expositio, in loc."). Jesus teaches us that over and above any human authority, even that of our parents, there is the primary duty to do the will of God. "And once we are consoled by the joy of finding Jesus--three days he was gone!--debating with the teachers of Israel (Lk 2:46), you and I shall be left deeply impressed by the duty to leave our home and family to serve our heavenly Father" ([St] J. Escriva, "Holy Rosary", Fifth Joyful Mystery"). See note on Mt 10:34-37.
50. We must remember that Jesus knew in detail the whole course his earthly life would take from his conception onwards (cf. note on Lk 2:52). This is shown by what he says in reply to his parents. Mary and Joseph realized that his reply contained a deeper meaning which they did not grasp. They grew to understand it as the life of their Child unfolded. Mary's and Joseph's faith and their reverence towards the Child led them not to ask any further questions but to reflect on Jesus' words and behavior in this instance, as they had done so on other occasions.
51. The Gospel sums up Jesus' life in Nazareth in just three words: "erat subditus illis", he was obedient to them. "Jesus obeys, and he obeys Joseph and Mary. God has come to the world to obey, and to obey creatures. Admittedly they were very perfect creatures--Holy Mary, our mother, greater than whom God alone; and that most chaste man Joseph. But they are only creatures, and yet Jesus, who is God, obeyed them. We have to love God so as to love his will and desire to respond to his calls. They come to us through the duties of our ordinary life--duties of state, profession, work, family, social life, our own and other people's difficulties, friendship, eagerness to do what is right and just" ([St] J. Escriva, "Christ Is Passing By", 17).
Jesus lived like any other inhabitant of Nazareth, working at the same trade as St Joseph and earning his living by the sweat of his brow. "His hidden years are not without significance, nor were they simply a preparation for the years which were to come after--those of his public life. Since 1928 I have understood clearly that God wants our Lord's whole life to be an example for Christians. I saw this with special reference to his hidden life, the years he spent working side by side with ordinary men. Our Lord wants many people to ratify their vocation during years of quiet, unspectacular living. Obeying God's will always means leaving our selfishness behind, but there is no reason why it should entail cutting ourselves off from the normal life of ordinary people who share the same status, work and social position with us.
"I dream--and the dream has come true--of multitudes of God's children, sanctifying themselves as ordinary citizens, sharing the ambitions and endeavors of their colleagues and friends. I want to shout to them about this divine truth: If you are there in the middle of ordinary life, it doesn't mean Christ has forgotten about you or hasn't called you. He has invited you to stay among the activities and concerns of the world. He wants you to know that your human vocation, your profession, your talents, are not omitted from his divine plans. He has sanctified them and made them a most acceptable offering to his Father" ([St] J. Escriva, "Christ Is Passing By", 20).
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.