Every year his parents went to Jerusalem for the Feast of Passover. When he was twelve years old, they went up to the Feast, according to the custom. After the Feast was over, while his parents were returning home, the boy Jesus stayed behind in Jerusalem, but they were unaware of it. Thinking he was in their company, they traveled on for a day. Then they began looking for him among their relatives and friends. When they did not find him, they went back to Jerusalem to look for him. After three days they found him in the temple courts, sitting among the teachers, listening to them and asking them questions. When his parents saw him, they were astonished. His mother said to him, "Son, why have you treated us like this? Your father and I have been anxiously searching for you."
"Why were you searching for me?" he asked. "Didn't you know I had to be in my Father's house?" But they did not understand what he was saying to them.
Then he went down to Nazareth with them and was obedient to them. But his mother treasured all these things in her heart. And Jesus grew in wisdom and stature, and in favor with God and men.
Luke 2:41-52 (NIV)