The number four hundred is the product of 8 and 50, and is a divinely perfect period.
"And he (Stephen) said, 'Brethren and fathers, listen: The God of glory appeared to our father Abraham when he was in Mesopotamia, before he dwelt in Haran, and said to him, 'Get out of your country and from your relatives, and come to a land that I will show you.' . . .
"'And God gave him no inheritance in it, not even enough to set his foot on. But even when Abraham had no child, He promised to give it to him for a possession, and to his descendants after him.
"'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.' " (Acts 7:2-3, 5-6, NKJV)
"Now when the sun was going down, a deep sleep fell upon Abram; and behold, horror and great darkness fell upon him. Then He (God) said to Abram: 'Know certainly that your descendants will be strangers in a land that is not theirs, and will serve them, and they will afflict them four hundred years . . .' " (Genesis 15:12-13, NKJV)