But in the fourth generation they shall come here again: for the iniquity of the Amorites is not yet complete.
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Ambrose of Milan
AD 397
The history of the Jews, who went down into Egypt and came out from Egypt, seems to accord with this. The years they spent there were , but not all of them lived a hundred years and more, as did Moses and Joshua, so that the time of the fourth generation would be appropriate in this context. So let us search rather for a mystical sense. In fact, the number four adapts well to all numbers, and it is in a certain sense the root and base of the decimal. It also represents the midpoint of the number seven. In fact, the ninetythird psalm is entitled “fourth day of the week” because this number is the intermediary between the first three and those that follow. In fact, three days precede it: the first, the second and the third; and three follow: the fifth, the sixth, the seventh. One who sings this psalm is proceeding through the life of this world, so to speak, in accordance with aptly placed numbers, like a quadrangle stable and perfect. In four books the Gospel is complete and perfect. Th...
What is clearly stated in the text can be expounded as follows. When the sun was already near setting, a flame emerged, and there appeared a smoking oven and fiery torches “that passed between the two parts of the divided animals,” burning and lighting up the place, to allow the patriarch to see what was happening and to reveal in a more divine manner the mysteries to be searched out. It should be noted that a fire did not appear only after the covenant had been made, but the gift of the law through Moses took place itself in the midst of a fire. Fire could be seen, and, without being able to see the one who was speaking, the giving of the commandments could be heard. What is suggested here is perhaps something like this. As the law contains rewards and punishments, it was given in the midst of fire to indicate that it brings burning to some and illumination to others. In fact, fire has a twofold power: it illuminates, and at the same time it burns. The gift of the law, then, burns tho...
After having said this of Abraham himself, God speaks of the children who will come from him: “In the fourth generation they shall come back here,” meaning the generation that would return to the land of inheritance. This is why he says that the return would take place after four hundred years, “because the iniquity of the Amorites is not yet complete”—iniquity for which they will suffer ruin, so that their condemnation will allow the descendants of Abraham to occupy their land. For God inflicts even chastisements with measure and in time, using patience until the time of retribution has arrived. There is a similar and edifying saying in the Gospel: “Then Jesus began to upbraid the cities where most of his mighty works had been done, because they did not repent: Woe to you, Chorazin! Woe to you, Bethsaida! For if the mighty works done in you had been done in Tyre and Sidon, they would have repented long ago in sackcloth and ashes.” To which one might object: Why then were the miracles ...
Fourth after the 400 years are finished; during which period of time, God was pleased to bear with those wicked nations; whose iniquity chiefly consisted in idolatry, oppression of the poor and strangers, forbidden marriages of kindred, and abominable lusts. (Leviticus xviii; Deuteronomy vi. and xii.) (Menochius)
