It was at twelve years old that Jewish boys came personally under the obligations of the law of Moses. Up to that age they had been treated as children, taught by their parents at home, but not yet expected to obey the harder precepts, such as fasting, or attending at Jerusalem at the three great feasts of the year. But at twelve years old they were called "Sons of the Law" or "Sons of the Precept;" and this signified that they now entered upon the second stage of life, and were no longer mere children. Henceforth they were old enough to have knowledge of their own, and to obey for themselves. When, therefore, our Lord was come to this age, Joseph and Mary, who had gone regularly up to Jerusalem in the former years by themselves, took, for the first time, their wonderful Child with them, not doubting that in this as in everything else, it was their duty to fulfil all righteousness that is, to obey the rules and orders of the law of God under which they lived.
I. Observe, first, that when the Lord is old enough, there is no question at all on the part of Mary and Joseph as to whether He shall be brought to Jerusalem for Jewish Confirmation. They did not doubt at all about it, they simply came at the due time to Jerusalem.
II. Still less did the heavenly Child Himself object. He was altogether obedient and dutiful to His mother, and to him who was called His father. No shadow of that wilfulness and uncorrected disobedience which we see so often in families, when boys and girls are allowed to do very much as they will, and judge for themselves whether they will do this thing or that, or whether they will refrain from it.
III. Observe how instantly our Lord feels that He is engaged in something higher now even than obedience to His earthly mother. It is His Father's business! Obedience to His mother has brought Him there, and fitted Him to come there. But now He is old enough to feel that he is engaged in God's business; in His heavenly Father's business. His brow is loftier. His look is changed. The sweet and dutiful Child has become, visibly, the Servant and Son of God. So I understand the words of the text, which says that they understood not the words which He spake unto them. They found Him altered; not less dutiful nor less sweet and obedient than before; but there was a loftier tone in His duty, and a deeper cause for His obedience, for He had begun to be, in His own Person, a Son of the Lord, and the obligation of His heavenly Father's business at once weighed upon His spirit and lifted it up.
G. Moberly, Plain Sermons at Brighstone,p. 12.