What does Luke 2:43 mean?
Deuteronomy 16:16 lists the feasts during which all eligible males were required assemble. Jesus' earthly family raised Him in obedience to the Law of Moses (Luke 2:21–22, 39). During one of these trips to Jerusalem, Jesus remains behind in the temple while his family's large travelling group begins the trip back to Nazareth. This will result in some tense searching and an eventual reunion (Luke 2:46).Modern readers may struggle to understand how Joseph and Mary could leave the city without Jesus, let alone not realize He is missing for an entire day (Luke 2:44). The fact that they travel in a party matters, since it's likely children and family rambled around within the group. In ancient culture, children also matured much more quickly than in modern societies—Jesus is nearly the traditional Jewish age of adulthood. Lastly—and most importantly—the Child in question is the only one in history to have never sinned (Hebrews 4:15; 1 Peter 2:22). Adults in His family would have every reason to trust Him, even if they weren't sure what He was doing at the time.
Scripture doesn't say that Jesus lied or ran away to stay in the city. How, exactly, His family misunderstood what was happening is not made clear, either. Though Mary initially thought Jesus was in the wrong (Luke 2:48, 50), Jesus seems to have thought His presence in the temple was obvious (Luke 2:49).
Luke 2:39–52 relates Scripture's only record of an event in Jesus' life occurring between His infancy and adulthood. His family travels to Jerusalem for a feast. When returning, Mary and Joseph lose track of Jesus, assuming He is with others in their large group. Once they realize He's missing, they find Him in the temple having a deep discussion with the teachers there. Jesus refers to the temple as His "Father's house," and the family returns to Nazareth. After this, Jesus grows and develops much the same as any other young boy.
The early part of this chapter is famously read at Christmas, while celebrating the birth of Jesus. Luke gives a relatively brief description of how Mary came to give birth in a stable, laying Jesus in a feeding trough. Nearby shepherds are informed of the news by multiple angels. Two people speak in praise of God at Jesus' circumcision. Years later, Joseph and Mary lose track of Jesus on the way back from Jerusalem, only to find Him astounding teachers in the temple with His wisdom.