The Lord said to Abram, after Lot had separated from him, “Raise your eyes now, and look from the place where you are, northward and southward and eastward and westward; for all the land that you see I will give to you and to your offspring forever. I will make your offspring like the dust of the earth; so that if one can count the dust of the earth, your offspring also can be counted. Rise up, walk through the length and the breadth of the land, for I will give it to you.” So Abram moved his tent, and came and settled by the oaks of Mamre, which are at Hebron; and there he built an altar to the Lord.
I find it really interesting that this promise comes after Abram more or less left this land allotment to chance and Lot’s choice. He let Lot choose what land he wanted, and then God pretty much says to Abram “everything else Lot didn’t choose is yours!” This becomes the Promised Land for the people of God. And it was essentially leftovers. Oh the tension between Providence and Human Action!