(10) Why was it said to him, “Thou shalt know to a certainty that thy seed shall be a stranger in a land that is not theirs, and shall be reduced to slavery, and shall be grievously afflicted for four hundred years?” (#Ge 15:13). That expression is admirably used, “It was said to him,” since a prophet is supposed to utter something, but yet he is not pronouncing any command of his own, but is only the interpreter of another who sends something into his mind; and moreover whatever he does utter and deliver in words is all true and divine. And in the first place, he declares that a family of the human race is to dwell in a land belonging to another; for all things which are beneath the heaven are the possession of God, and those living creatures which exist on the earth may more properly and truly be said to be sojourners in a foreign land than to be dwelling in a country of their own which by nature they have not got. In the second place, he thus declares to us that every mortal is a slave after his kind. But no man is found to be free, but every one has many masters who vex and afflict him both within and without; for instance, without there are the winter which affects him with the cold, the summer which scorches him with heat, and hunger, and thirst, and many other calamities; and within there are pleasures and concupiscences, and sorrows, and fears. But his servitude is limited to a period of four hundred years, during which the aforesaid pleasures shall rise up against him. On which account it has been said above, that Abraham passed over and sat upon them, hindering and repelling them; as far as the literal words go, repelling those carnivorous birds which were hovering over the divided animals, but in fact repelling the afflictions which come upon men. Since a man who is in his own proper nature a lover of, and also by diligent practice a studier of virtue, is a most humane physician of our race, and a true protector of it, and guardian of it from evil. For all these things have an allegorical reference to the soul. For while the soul of the wise man, descending from above from the sky, comes down upon and enters a mortal and is sown in the field of the body, it is truly sojourning in a land which is not his own. Since the earthly nature of the body is wholly alien from pure intellect, and tends to subdue it and to drag it downwards into slavery, bringing every kind of affliction upon it, until the sorrow, bringing the attractive multitude of vices to judgment, condemns them; and thus at last the soul is restored to freedom. And it is on this account that he subsequently adds the sentence, “Nevertheless the nation which they shall send I will judge: and afterwards they shall go forth with great substance;” namely, with the same measure, and still better. Because then the mind is released from its mischievous colleague, departing out of the body and being transferred not only with freedom but also with much substance; so as to leave nothing good or useful behind to its enemies. Since every rational soul is productive, but he who thinks himself loaded and endued with virtue in his own counsel, is unable to preserve his fruit unto the end. For it becomes a virtuous man to attain to the objects which he has intended of his own accord, as also the counsels of wisdom correspond to those objects. Since, as some trees, although they appear productive at the first season of the budding of their fruits, are yet unable to bring them to maturity, so that the whole fruit before it becomes ripe is shaken off by every trifling cause; in the same manner the souls of inconstant men feel many influences which contribute to their productiveness, but nevertheless are unable to keep them sound till they arrive at perfection, as a man studious of virtue ought to do in order eventually to gather them as his own possessions.