Genesis 15:18
“In the same day the LORD made a covenant with Abram, saying, To your seed have I given this land, from the river of Egypt to the great river, the river Euphrates:”
Here the Lord made (cut) a covenant with Abram, which He confirmed by passing between the pieces of his (Abram’s) sacrifice (v.17) saying, “Unto thy seed have I given this land, from the river of Egypt to the river Euphrates.” Thus, a huge tract of real estate would belong to his children's children.
Abram didn't know it at the time but he would have two principal sons, Isaac and Ishmael, and the descendants of those two, dispute possession of the lands to this day - the Jews and the Arabs.
As to whose land the promise is directed to, it’s important to see God's words to Isaac in Genesis 26:3 - "I will be with you and will bless you, for to you and to your offspring I will give all these lands, and I will establish the oath that I swore to Abraham your father.”
God loved (loves) both sons, but the promise is to Isaac and his son, Jacob, also known as Israel – and He keeps His promises.
The Truth
“He remembers His covenant forever, the Word which He commanded, for a thousand generations, The covenant which He made with Abraham, and His oath to Isaac, and confirmed it to Jacob for a statute, to Israel as an everlasting covenant, Saying, “To you I will give the land of Canaan as the allotment of your inheritance,” (Psalm 105:8-11)
Believe in the Lord, as Abraham did (Genesis 15:6), and God will bless you and fulfill the desires of your heart - forever.