Acts 7:6

6 God spoke to him in this way: ‘For four hundred years your descendants will be strangers in a country not their own, and they will be enslaved and mistreated.

Read Acts 7:6 Using Other Translations

And God spake on this wise, That his seed should sojourn in a strange land; and that they should bring them into bondage, and entreat them evil four hundred years.
And God spoke to this effect--that his offspring would be sojourners in a land belonging to others, who would enslave them and afflict them four hundred years.
God also told him that his descendants would live in a foreign land, where they would be oppressed as slaves for 400 years.