Genesis 16:8

Moreover, when the beauty of the spiritual law is illuminated, that which is no more than shadow flees. Sacrifices that are luminous compared with those of "the shadow" were in fact announced in the transmitted teaching and have been effectively introduced in practice. Likewise too "that which was only partial" is abolished when that which is perfect is present. A case of "fleeing far from the face" is the one who, on hearing the Lord say, you must "be born from above," inquires, "How can a man be born when he is old?" for he is interpreting a divine saying in human terms.

From this text one gains insight into the virtue of Hagar as well, and one becomes aware that she is a woman not to be despised since an angel converses with her and shows concern for her that is hardly superficial, for it is evidently by the will of God that [the angel speaks]. It is not at all improbable that Hagar was a person of zeal, because she was chosen by the holy woman Sarah to sleep with Abraham. Her nobility of soul is likewise shown by the fact that she says, "I am fleeing from my mistress, Sarah," without saying anything bad about her. We earlier had hypothesized that Sarah represented virtue and a spiritual understanding of the Scriptures but that Hagar represented the introductory knowledge and the shadow. One who approaches the divine teaching should listen to Scripture in such a way as to understand it first according to the letter, while grasping its spirit gradually and in due order.Sarah's child therefore requires an introductory course so that by this means he might reach the more perfect things. Similarly it would be said of the Israelites that they were "the first to whom the oracles of God were entrusted," which were given to them "until the time of correction." No one, in fact, who remains trapped in the letter and at the introductory level can claim Wisdom itself. If then lovers of Wisdom, who make use of what belongs to the introductory level, should remain there, they are in a sense despising virtue, but if they return to better sentiments, they put aside the introductory method so that it makes a kind of flight. For once progress has arrived, the earlier things pass away. That which has been the possession of Hagar the Egyptian is transcended. It is to earthly examples that the introductory teaching appeals for support.… The angel then, having found her fleeing because of the greatness of virtue, makes her retrace her steps. The word of the Master indeed causes even what belongs to the introductory exercises to redound to virtue.… The virtuous one must in fact know the principles and the goal, while the one who is still at the introductory stage often remains at this level under the pretext that virtue is too high. He flees, as it were, the effort required by perfection. This is what is revealed in the statement "I am fleeing from Sarah, my mistress."