But when the fullness of the time had come, God sent forth His Son, born of a woman, born under the law, to redeem those who were under the law, that we might receive the adoption as sons. Galatians 4:4–5 NKJV
Think of it: the Son is sent to win sons! Oh! It is wonderful.
Now you might ask, What do you mean by “the fullness of the time”? Well, it was clearly the moment when the probation of man was over. The first man had had a fair, full, and complete trial. Tried in innocence, he had fallen and become guilty: tried without law, he was lawless: tried under the law, he had broken it. God had one resource left, the secret thought of His heart from eternity: it was to send into this scene His own Son. His own beloved Son became man, that, as man, He might bless and redeem man, fallen man, and bring him to God. Man with all his learning, all his inventions, all his searching, had not found out God. He had lost God through the fall, the fruit of sin, and he never found Him again. Even the law did not meet his case, for the law was not the revelation of God: the law was the declaration of what man ought to be, not the revelation of what God is.
You may turn round and say to me, “But did not man know God in creation?” To a certain extent, clearly, and therefore he is without excuse, as the apostle puts it in Romans 1:20. His eternal power and Godhead are most surely to be known in creation, but that is not what He Himself is.
“No one has seen God at any time. The only begotten Son, who is in the bosom of the Father, He has declared Him” (Jn. 1:18). If there be a man who supposes that he can learn to know God apart from this Blessed One, depend upon it, my friend, you are profoundly mistaken.