The 400 years prophecy to Abraham doesn’t seem to fit the details mentioned in the Torah. This blog is to explain the problem and provide a plausible solution only using authoritative texts.
(Gen 15:8,13-16) And he said, “Lord GOD, how shall I know that I will inherit it?” … Then the LORD said to him, “Know for certain that for four hundred years your descendants will be strangers in a country not their own and that they will be enslaved and mistreated there. But I will punish the nation they serve as slaves, and afterward they will come out with great possessions. You, however, will go to your ancestors in peace and be buried at a good old age. In the fourth generation your descendants will come back here, for the sin of the Amorites has not yet reached its full measure.”
Acts 7:6 “But God spoke in this way: that his descendants would dwell in a foreign land, and that they would bring them into bondage and oppress them four hundred years.
Gen 15:3 Then Abram said, “Look, You have given me no offspring; indeed one born in my house is my heir!” … 5 Then He brought him outside and said, “Look now toward heaven, and count the stars if you are able to number them.” And He said to him, “So shall your descendants be.” … 13-16 Then the LORD said to him, “Know for certain that for four hundred years your descendants will be strangers in a country not their own and that they will be enslaved and mistreated there. But I will punish the nation they serve as slaves, and afterward they will come out with great possessions. You, however, will go to your ancestors in peace and be buried at a good old age. In the fourth generation your descendants will come back here, for the sin of the Amorites has not yet reached its full measure.”