When did God make the covenant with Abram saying 'unto thy seed I have given'?
God made the covenant with Abram in the same day He consummated the transfer of the title deed to Abraham. The phrase 'unto thy seed I have given' uses past tense, indicating the land was already given and accomplished in the preceding verses.
Les explains that in the same day God consummated this transfer of title deed to Abraham, the Lord Jehovah made a covenant with Abram, saying, 'unto thy seed I have given.' The verb is past tense—it is done, accomplished back in the previous verses. God deeded the land from the river of Egypt to the great river Euphrates, along with all the tribes geographically at that time: the Parasites, Amorites, Canaanites, Girgashites, and Jebusites. This was God's title deed to the Middle East for the nation of Israel.
In the same day the LORD made a covenant with Abram, saying, Unto thy seed have I given this land, from the river of Egypt unto the great river, the river Euphrates: