XIII. (43) But we must begin our explanation of these mysteries in this way. A husband unites with his wife, and the male human being with the female human being in a union which tends to the generation of children, in strict accordance with and obedience to nature. But it is not lawful for virtues, which are the parents of many perfect things, to associate with a mortal husband. But they, without having received the power of generation from any other being, will never be able by themselves alone to conceive any thing. (44) Who, then, is it who sows good seed in them, except the Father of the universe, the uncreated God, he who is the parent of all things? This, therefore, is the being who sows, and presently he bestows his own offspring, which he himself did sow; for God creates nothing for himself, inasmuch as he is in need of nothing, but he creates every thing for him who is able to take it. (45) And I will bring forward as a competent witness in proof of what I have said, the most holy Moses.{14}{#ge 21:1.} For he introduces Sarah as conceiving a son when God beheld her by himself; but he represents her as bringing forth her son, not to him who beheld her then, but to him who was eager to attain to wisdom, and his name is called Abraham. (46) And he teaches the same lesson more plainly in the case of Leah, where he says that “God opened her Womb.”{15}{#ge 29:13.} But to open the womb is the especial business of the husband. And she having conceived, brought forth, not to God, for he alone is sufficient and all-abundant for himself, but to him who underwent labour for the sake of that which is good, namely, for Jacob; so that in this instance virtue received the divine seed from the great Cause of all things, but brought forth her offspring to one of her lovers, who deserved to be preferred to all her other Suitors.{16}{#ge 25:21.}