And when Abram asked whereby he might know that he should inherit it, God said to him, "Take me an heifer of three years old, and a she-goat of three years old, and a ram of three years old, and a turtle-dove, and a pigeon. And he took unto him all these, and divided them in the midst, and laid each piece one against another; but the birds divided he not. And the fowls came down," as it is written, "on the carcasses, and Abram sat down by them. But about the going down of the sun, great fear fell upon Abram; and, lo, an horror of great darkness fell upon him. And He said unto Abram, Know of a surety that thy seed shall be a stranger in a land not theirs, and they shall reduce them to servitude and shall afflict them four hundred years: but the nation whom they shall serve will I judge; and afterward shall they come out hither with great substance. And thou shalt go to thy fathers in peace; kept in a good old age. But in the fourth generation they shall come hither again: for the iniquity of the Amorites is not yet full. And when the sun was setting, there was a flame, and a smoking furnace, and lamps of fire, that passed through between those pieces. In that day the Lord made a covenant with Abram, saying, Unto thy seed will I give this land, from the river of Egypt unto the great river Euphrates: the Kenites, and the Kenizzites, and the Kadmonites, and the Hittites, and the Perizzites, and the Rephaims, and the Amorites, and the Canaanites, and the Hivites, and the Girgashites, and the Jebusites." 
All these things were said and done in a vision from God; but it would take long, and would exceed the scope of this work, to treat of them exactly in detail. It is enough that we should know that, after it was said Abram believed in God, and it was counted to him for righteousness, he did not fail in faith in saying, "Lord God, whereby shall I know that I shall inherit it?" for the inheritance of that land was promised to him. Now he does not say, How shall I know, as if he did not yet believe; but he says, "Whereby shall I know," meaning that some sign might be given by which he might know the manner of those things which he had believed, just as it is not for lack of faith the Virgin Mary says, "How shall this be, seeing I know not a man?"  for she inquired as to the way in which that should take place which she was certain would come to pass. And when she asked this, she was told, "The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee."  Here also, in fine, a symbol was given, consisting of three animals, a heifer, a she-goat, and a ram, and two birds, a turtle-dove and pigeon, that he might know that the things which he had not doubted should come to pass were to happen in accordance with this symbol. Whether, therefore, the heifer was a sign that the people should be put under the law, the she-goat that the same people was to become sinful, the ram that they should reign (and these animals are said to be of three years old for this reason, that there are three remarkable divisions of time, from Adam to Noah, and from him to Abraham, and from him to David, who, on the rejection of Saul, was first established by the will of the Lord in the kingdom of the Israelite nation: in this third division, which extends from Abraham to David, that people grew up as if passing through the third age of life), or whether they had some other more suitable meaning, still I have no doubt whatever that spiritual things were prefigured by them as well as by the turtle-dove and pigeon. And it is said, "But the birds divided he not," because carnal men are divided among themselves, but the spiritual not at all, whether they seclude themselves from the busy conversation of men, like the turtle-dove, or dwell among them, like the pigeon; for both birds are simple and harmless, signifying that even in the Israelite people, to which that land was to be given, there would be individuals who were children of the promise, and heirs of the kingdom that is  to remain in eternal felicity. But the fowls coming down on the divided carcasses represent nothing good, but the spirits of this air, seeking some food for themselves in the division of carnal men. But that Abraham sat down with them, signifies that even amid these divisions of the carnal, true believers shall persevere to the end. And that about the going down of the sun great fear fell upon Abraham and a horror of great darkness, signifies that about the end of this world believers shall be in great perturbation and tribulation, of which the Lord said in the gospel, "For then shall be great tribulation, such as was not from the beginning." 
But what is said to Abraham, "Know of a surety that thy seed shall be a stranger in a land not theirs, and they shall reduce them to servitude, and shall afflict them 400 years," is most clearly a prophecy about the people of Israel which was to be in servitude in Egypt. Not that this people was to be in that servitude under the oppressive Egyptians for 400 years, but it is foretold that this should take place in the course of those 400 years. For as it is written of Terah the father of Abraham, "And the days of Terah in Haran were 205 years,"  not because they were all spent there, but because they were completed there, so it is said here also, "And they shall reduce them to servitude, and shall afflict them 400 years," for this reason, because that number was completed, not because it was all spent in that affliction. The years are said to be 400 in round numbers, although they were a little more, -- whether you reckon from this time, when these things were promised to Abraham, or from the birth of Isaac, as the seed of Abraham, of which these things are predicted. For, as we have already said above, from the seventy-fifth year of Abraham, when the first promise was made to him, down to the exodus of Israel from Egypt, there are reckoned 430 years, which the apostle thus mentions: "And this I say, that the covenant confirmed by God, the law, which was made 430 years after, cannot disannul, that it should make the promise of none effect."  So then these 430 years might be called 400, because they are not much more, especially since part even of that number had already gone by when these things were shown and said to Abraham in vision, or when Isaac was born in his father's 100th year, twenty-five years after the first promise, when of these 430 years there now remained 405, which God was pleased to call 400. No one will doubt that the other things which follow in the prophetic words of God pertain to the people of Israel.
When it is added, "And when the sun was now setting there was a flame, and lo, a smoking furnace, and lamps of fire, which passed through between those pieces," this signifies that at the end of the world the carnal shall be judged by fire. For just as the affliction of the city of God, such as never was before, which is expected to take place under Antichrist, was signified by Abraham's horror of great darkness about the going down of the sun, that is, when the end of the world draws nigh, -- so at the going down of the sun, that is, at the very end of the world, there is signified by that fire the day of judgment, which separates the carnal who are to be saved by fire from those who are to be condemned in the fire. And then the covenant made with Abraham particularly sets forth the land of Canaan, and names eleven tribes in it from the river of Egypt even to the great river Euphrates. It is not then from the great river of Egypt, that is, the Nile, but from a small one which separates Egypt from Palestine, where the city of Rhinocorura is.