Jesus walked upon this earth as wisdom personified. So how is it that He grew in wisdom? The answer no doubt lies in His State of Humiliation. The Son of God became flesh and entered His State of Humiliation, wherein He did not 
fully or always use the divine powers communicated to His human nature. One aspect of this is that as a “regular” human He had to grow, and He did not use His divine powers to enhance this growth. Sunday’s Gospel describes His growth: And Jesus increased in wisdom and in stature and in favor with God and man.
He had to grow physically (“in stature”), for when He entered this world He started, like you and me, as a mere zygote. And being nourished like other babies in utero, He grew in the womb, then, nourished as all other humans, He grew as a child and ultimately He reached full manhood. He also had to grow in His relationships with others (“in favor with God and man”). He thus grew in His relationship to God, to family, to His immediate neighbors, to His fellow Jews and in His relationships to foreigners (such as the Romans) whom He encountered outside of Judaism. Thirdly He had to grow in knowledge and wisdom. The omniscient Son of God who could enter His State of Humiliation by virtue of His incarnation, had to be “schooled” by parents and rabbis, and as He thus grew in knowledge He—the one called wisdom in the Old Testament—grew in His wisdom…which especially included His fear, love and trust toward God, which was reflected in His relation to His neighbor.
It is apparent from Sunday’s Gospel that at age twelve Jesus knew His identity as the Son of God, for He asks His parents, Did you not know that I must be in my Father’s house? Many have asked, “When and how did Jesus realize this identity as the eternal Son of God?”
Though we have no definitive answer to this, it seems apparent that—consistent with the aspects of His State of Humiliation—Jesus came to realize the fullness of His identity from His growth in God’s Word (our Old Testament). No doubt Mary informed Him of His miraculous conception and of God’s Word to her, but then as He was schooled in the Scriptures He soon came to realize that these Holy Writings are about Him. Certainly at His Baptism the Father revealed His eternal Sonship. However, consistent with His State of Humiliation, He had already grown into this understanding. For as He grew in wisdom, having also perfect understanding and a perfectly working mind, He—through the same Scripture that reveals God’s wisdom to us—fully grasped and remembered every prophecy and jot and tittle of Holy Scripture. Since the Scriptures were primarily about the Messiah, Jesus at some point realized—through the same Word by which Timothy realized the Christ (2 Timothy 3:15)—that He is the long awaited Christ, God’s eternal Son.
Not only did the Lord Jesus realize His eternal identity, but He realized His destiny as mankind’s Savior. From that very Temple where Jesus walked as a child of twelve, and in which He would hold forth also as an adult, Jesus Christ understood perfectly all the aspects of sacrifice, and with His perfect grasp of all biblical knowledge, he realized that these sacrifices in His Father’s house were perfectly portraying the sacrifice of Himself—in fact that was their purpose. From the Jewish Scriptures He knew that He must be crucified. Thus for us he has appeared once for all at the end of the ages to put away sin by the sacrifice of himself (Heb. 9:26). Now in Him wisdom has been imparted to us, for He and His work of salvation bespeak and embody true wisdom.