Genesis 15:18 - Matthew Poole's English Annotations on the Holy Bible

Unto thy seed have I given this land, i.e. decreed and promised in due time to give, which makes it as sure as if it were actually given to them. Or, I will give; words of the past time being oft put for the future, especially in prophecies. The river of Egypt; not Nilus, which elsewhere is so called, but a less river, as is sufficiently implied, because this is opposed to the great river here following; but a river called Sihor, which divides Egypt from Canaan. See Numbers 34:5 Joshua 13:3 1 Chronicles 13:5. The accomplishment hereof, see 2 Samuel 8:3 1 Kings 4:21, 1 Kings 9:21.