"On the Incarnation of the Word" is a treatise by St. Athanasius (written around 318 AD as a continuation of the similar "Against the Heathen"), which extensively discusses the incarnation of the Word of God. Starting from the creation of the world out of nothing, it develops the topics related to the fall of the first-created beings, the misery that followed because humans disregarded spiritual matters and clung to material goods, as well as their separation from God, which would result in their destruction through physical and spiritual death. God took care of humanity by revealing Himself through His creation, the giving of the Law, and the sending of the Prophets.
And because these things were not sufficient, the Word of God Himself became incarnate. He took on a body that could die in order to make it, through His resurrection, immortal. He defeated the demons and restored humanity to saving truth. He became human so that we might become divine. The purified soul, free from passions, can comprehend this truth.