41Now his parents went to Jerusalem every year at the Feast of the Passover. 42And when he was twelve years old, they went up according to custom. 43And when the feast was ended, as they were returning, the boy Jesus stayed behind in Jerusalem. His parents did not know it, 44but supposing him to be in the group they went a day’s journey, but then they began to search for him among their relatives and acquaintances, 45and when they did not find him, they returned to Jerusalem, searching for him. 46After three days they found him in the temple, sitting among the teachers, listening to them and asking them questions. 47And all who heard him were amazed at his understanding and his answers. 48And when his parents 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 searching for you in great distress." 49And he said to them, "Why were you looking for me? Did you not know that I must be in my Father’s house?" 50And they did not understand the saying that he spoke to them. 51And he went down with them and came to Nazareth and was submissive to them. And his mother treasured up all these things in her heart. 52And Jesus increased in wisdom and in stature and in favor with God and man.
---->There are so many perplexing stories in the Bible, so many stories that make you scratch your head and say, "What!?" Luke's account of the 12 year-old Jesus in the temple, teaching the rabbis, is certainly one of the more exceptionally bizarre stories. For one thing, Luke writes the only Biblical account of this story—for whatever reason, Matthew, Mark, and John all decided that this particular happening wasn't of much consequence. Therefore, it stands as the only account of Jesus's transition from babyhood to adulthood. And, in typical Luke fashion, it is written tremendously when read at a more critical level, as it is the "median," if you will, of his life and combines elements of his infancy and elements of his adulthood. The implication here, of course, is that this is the exact middle of his life, when he is a child, but putting away childish things; he is not yet an adult, but he is starting to develop the worldview of an adult and a more adult image of himself.
First of all, and I'll never understand how this happened, Joseph and Mary managed to lose their son after their pilgrimage to Jerusalem. That's the part of this story that makes it so wildly bizarre—how in the world do you lose your son? How in the world did they manage to lose the Son of God!? Can you imagine the sheer panic that must have been coursing through their veins on Day 2 of the journey home when they suddenly realized, "Oh, wait—where's Jesus??" So they have to go back to Jerusalem and, after three days of searching for him (don't you love foreshadowing...?), they find their 12 year-old son, Jesus, preaching to the rabbis! What!? Furthermore, according to verse 47, the rabbis were actually "amazed" at his understanding of the Scriptures!
Mary, as we can imagine, is relieved and disappointed at the same time, and asks, "Son, why have you treated us like this? Your father and I have been worried sick about you!" Obviously! As parents, they had every right to be mad at Jesus (even though their anger seems more like a projection of their own guilt—they're the ones, after all, who somehow managed to leave the Messiah behind).
Isn't it amazing how quickly we get angry at God, even when our struggles are of our own doing?
Then, in stark contrast to Mary's hysterics, Jesus very calmly answers her, "Why were you looking for me? Did you not know that I must be in my Father's house" (other translations read "about my Father's business"). This is significant for three reasons: 1) they are Jesus's first recorded words, 2) he refers to God as "Father" and, thus, creates a new way for humanity to view God, and 3) they provide an element of the "discipleship" concept, what we will find become one of Jesus's main preaching points.
The fact that they are his first recorded words tell us this: Luke wants his readers to know that doing his Father's work is at the forefront of Jesus's mind. There was no allegiance to things of the world on his part, and there was no hidden agenda on his part. He wasn't concerned with what people would think of him, he wasn't concerned with the reactions people would have to him, and he wasn't concerned with the repercussions that would come from separating himself from his family. His one and only concern was being about his Father's business.
And it's absolutely critical to note that Jesus refers to God as his "Father" when Mary says, "...your father and I..." Here, Jesus is clearly separating himself from humanity, separating himself from familial ties, and separating himself from societal norms. Here, Jesus is explaining to his parents that they are not his ultimate authority, and pleasing them, or even obeying them, is not his ultimate goal. His ultimate goal is to be doing the work of his heavenly Father. Jesus will bring this concept up again later in Luke as he addresses it more directly:
What Jesus is talking about here is discipleship—it is a foreshadowing of things to come on Luke's part. By telling the story of Jesus staying in Jerusalem, separating himself from his family, and then answering them so casually and matter-of-factly, and by making his response his very first recorded words, Luke is illustrating that ministry—being about our Father's business—should be at the very forefront of our efforts. No matter what we do in life, we should be doing it with the mindset "How does this further the Kingdom? Is this me being about my Father's business?"" 49I came to cast fire on the earth, and would that it were already kindled! 50I have a baptism to be baptized with, and how great is my distress until it is accomplished! 51Do you think that I have come to give peace on earth? No, I tell you, but rather division. 52For from now on in one house there will be five divided, three against two and two against three. 53They will be divided, father against son and son against father, mother against daughter and daughter against mother, mother-in-law against her daughter-in-law and daughter-in-law against mother-in-law." (Luke 12:49-53)
And by clearly differentiating between Jesus's earthly father (Joseph) and his heavenly Father (Jehovah), Luke is illustrating a point that Jesus will bring up later—being about our Father's business means separating ourselves from all things of the world. It means having no reservations about the sacrifices we have to be willing to make. It may mean separation from our families (Luke 12:49-53, 14:25-26), it may mean facing unjust hardships (14:27), it may mean losing everything (14:33, 9:25), and may it even mean losing your life (9:23-24)!
This is the sort of discipleship Jesus was calling himself to, and this is the cost of discipleship that we are called to.