Genesis 15:16

in the fourth generation This agrees with the genealogy in Exodus 6:16-20, where the generations are: (1) Levi, (2) Kohath, (3) Amram, (4) Moses. If the fourth generation is to be harmonized with the 400 years in Genesis 15:13, a generation must have been computed as 100 years. Isaac was born in Abram's 100th year. But it may be doubted, whether the mention of "the fourth generation" comes from the same hand as "the 400 years" in Genesis 15:13.

for the iniquity of the Amorite The idea is that the wickedness of the people of Canaan must reach a certain degree, before the Divine penalty can be inflicted. The postponement of the penalty, which indicates Divine forbearance, means also a terrible, but gradual, accumulation of guilt. For the iniquity of the Amorites, cf. Genesis 13:13; Leviticus 18:24-30; Deuteronomy 9:5. On the Amorite, see Genesis 10:16.