Leo the Great

There was only one remedy in the secret of the divine plan that could help the fallen living in the general ruin of the entire human race. This remedy was that one of the sons of Adam should be born free and innocent of original transgression, to prevail for the rest by his example and by his merits. This was not permitted by natural generation. There could be no clean offspring from our faulty stock by this seed. The Scripture says, "Who can make a clean thing conceived of an unclean seed? Isn't it you alone?" David's Lord was made David's Son, and from the fruit of the promised branch sprang. He is one without fault, the twofold nature coming together into one person. By this one and the same conception and birth sprung our Lord Jesus Christ, in whom was present both true Godhead for the performance of mighty works and true manhood for the endurance of sufferings.