What does Luke 2:51 mean?
Mary does not understand everything which happens to her with perfect knowledge. Like anyone else, she would have had moments of doubt, confusion, or misunderstanding. One such incident is her frustration when a twelve-year-old Jesus is accidentally left behind in Jerusalem, only to be found three days later in the temple (Luke 2:41–47). Though Mary is upset that He "mistreated" her (Luke 2:48), He reassures her that the temple is the only place she should have expected Him to be.In response to this, Mary once again is said to pay special attention. That she "treasures" what is happening implies that she deliberately chooses to remember it—holding it in her mind as something worth maintaining. This is the same way she reacted when shepherds arrived to see the newborn Jesus (Luke 2:19). Though she does not understand, at first (Luke 2:50), she remains open to the work of God in her life (Luke 1:38).
Luke's comment here about Jesus' submission resolves several interesting debates about the Bible and Jesus' early life. His remark does not suggest that Jesus was, only now, after the incident in the temple, being submissive to His parents. Rather, it seems Luke is clarifying that Jesus' attitude continued to be submissive. His remaining in the temple wasn't an act of rebellion. It was not careless. When His family arrived and wanted Him to leave, He did so, as part of a pattern of godly obedience (Exodus 20:12).
This remark also helps to clarify that submission in no sense implies inferiority. Jesus is God incarnate (John 1:1, 14)—He is literally the divine Creator and Master of the very parents to whom He submits. When Scripture speaks of submission between any two persons, such as within a marriage (Ephesians 5:22–24; Titus 2:9; 3:1; Hebrews 13:17), it allows no condescension from one to the other.