Genesis 16:6

There is a kind of maltreatment of the slave girl that we have likened, by anagogy, to the preparatory exercises (progymnasmata): the shadow [Hagar] of things to come [the generative promise] is transcended. For one who is hastening toward perfection no longer needs that which is preparatory. This is why it is quite natural that the slave girl should flee, because what belongs to the introductory level no longer remains when progress and perfection have arrived.

In the literal sense, this statement introduces the beginner to the passionlessness (apatheia) of the patriarch, who had received the slave girl from his wife without looking for pleasure and who now yields to his wife and withdraws in accordance with her wishes. As for the spiritual sense, the zealous man, even if he is still at the introductory level, since he is not altogether a stranger to virtue, receives with pleasure her reproaches and thus more rapidly abandons the petty things. As one who submits to her, he follows her directions in the use of the preparatory exercises and allows her to control them. Since he is desirous to make virtue the goal of all his words, actions and thoughts, he willingly accepts any corrections that come from her.

And here follow the times of Abraham's sons, the one by Hagar the bondmaid, the other by Sarah the free woman, about whom we have already spoken in the previous book. As regards this transaction, Abraham is in no way to be branded as guilty concerning this concubine. For he dealt with her for the begetting of progeny, not for the gratification of lust, and not to insult but rather to obey his wife, who supposed it would be solace of her barrenness if she could make use of the fruitful womb of her handmaid to supply the defect of her own nature. By that law of which the apostle says, "Likewise also the husband has not power of his own body, but the wife," Sarah could, as a wife, do benefit to him through childbearing by another, when she could not do so in her own person. Here there is no wanton lust, no crude lewdness. The handmaid is delivered to the husband by the wife for the sake of progeny and is received by the husband for the sake of progeny, each seeking not guilty excess but natural fruit. Then the pregnant bondwoman despised her barren mistress, and Sarah, with womanly jealousy, rather laid the blame of this on her husband. Yet even then Abraham showed that he was not a slavish lover but a free begetter of children and that in using Hagar he had guarded the chastity of Sarah his wife and had gratified her will and not his own. He had received her without seeking her, gone in to her without being attached, impregnated without loving her. For he says, "Behold, your maid is in your power; do to her as you please." Here is a man able to treat different women as they require—his wife temperately, his handmaid compliantly, neither intemperately!