For Israel, the time of childhood training under the law came to an end when God sent forth his Son into the world. ‘The fullness of the time was come.
For our sakes the giver of the Ten Commandments placed himself under his own law and undertook to keep it perfectly. He who freely and willingly does only what is right and good and true and holy, because his character is unchangeably holy and he can do nothing else, in an act of immeasurable condescension placed himself under an obligation to obey the commands he had given to mankind. Although he was truly a man, he was the head of a different covenant to the first Adam and was free from the obligations of the first Adam, but for our sakes he placed himself under the law. Because he had come to redeem us, he had to take on our obligations before God and to make himself fully answerable for us as our surety.
At the very hour that God had determined, not a moment too soon or too late Christ was born into our world. But why did so long a period of time pass after the fall before the Christ was sent into the world and the Gospel preached to the nations? Scripture does not answer this question directly, but we see how God filled this time. God will not give his glory to another, and mankind had to learn that the greatest struggles of the human mind for wisdom and understanding were fruitless until God revealed his salvation from heaven. All the efforts of Greek philosophy to explain the nature of reality, how we know what we know, and how we should live our lives failed to provide answers that were lasting and satisfactory. In the meantime Israel was led along a path that would instruct the entire human race.