God told Abraham that later on he would deliver his descendants from Egypt.

Acts 7:6-7

6 “Later God told Abraham, ‘Your descendants will go and live in a foreign country. They will live there for 400 years, and during that time their leaders will mistreat your descendants and force them to work as slaves.’ 7 But God also said, ‘I will punish the people who make them work as slaves. Then, after that, your descendants will leave that land and they will come and worship me in this land.’ ”