God told him that his descendants would be foreigners in a strange land, and that they would be enslaved and mistreated four hundred years.
KJV
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.
ASV
And God spake on this wise, that his seed should sojourn in a strange land, and that they should bring them into bondage, and treat them ill, four hundred years.