Ellicott's Commentary for English Readers - Genesis 15:14
(14) That nation.—Had it been expressly revealed that the country that would afflict them was Egypt, the patriarchs might have been unwilling to go thither; but the reference to the plagues in the denunciation of judgment, and to the spoiling of the Egyptians in the promise that they should “come out with great substance” (Exodus 12:36), gave detail sufficient for future guidance, and for their assurance in time to come that the promise had been fulfilled. read more
Ellicott's Commentary for English Readers - Genesis 15:13
(13) Four hundred years.—The exact duration of the sojourn in Egypt was 430 years (Exodus 12:40-41), and with this agrees the genealogy of Jehoshua (1 Chronicles 7:23-27). read more