Like many before and after him, Anselm, the great medieval theologian, raised and answered this question. In his epochal work, Cur Deus Homo, he wrote, “No one, however, ought to make satisfaction for the sin of man except man; and no one can make this satisfaction except God Himself. He who makes satisfaction for human sin must therefore be God-man.”
Here is the idea. Because God is infinitely just, a man had to atone for the sins committed by man. But, because God is also infinitely holy, no one but God himself could make satisfaction to God for the infinite weight of human sin. Therefore, God had to become flesh.
Anselm’s crucial proposition is a window through which we see the infinite greatness of both God’s justice and his love. Both had to be satisfied, and God was willing to become man to get the job done.
Rejoice! This is no small God. It is the God we worship during this holiday season.