Adam Clarke on Luke 2:41

His parents went - every year - This was their constant custom, because positively enjoined by the law, Exo 23:17. But it does not appear that infants were obliged to be present; and yet all the men-children are positively ordered to make their appearance at Jerusalem thrice in the year, Exo 34:23. And our Lord, being now twelve years old, Luk 2:42, accompanies his parents to the feast. Probably this was the very age at which the male children were obliged to appear before the Lord at the three public festivals - the feast of unleavened bread, of weeks, and of tabernacles. According to the Jewish canons, it was the age at which they were obliged to begin to learn a trade.