Adam Clarke on Acts 7:6

That his seed should sojourn in a strange land - See Gen 15:13, Gen 15:14.

Four hundred years - Moses says, Exo 12:40, that the sojourning of the children of Israel in Egypt - was 430 years. See the note there. St. Paul has the same number, Gal 3:17; and so has Josephus, Ant. lib. ii. cap. 1, sect. 9; in Bell. lib. v. cap. 9, sect. 4. St. Stephen uses the round number of 400, leaving out the odd tens, a thing very common, not only in the sacred writers, but in all others, those alone excepted who write professedly on chronological matters.