Genesis 15:18
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: 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:
In the same day the Lord made a covenant with Abram to give Canaan to his seed, with its boundaries stretching from the river of Egypt unto the great river Euphrates. The covenant was pledged when symbols of God's presence passed between the sacrificed animals. Possession was not to be immediate, but was to come at the appointed time only after a period of suffering for his descendants and after centuries of waiting.
The delay occurred because the iniquity and guilt of the Amorites had not yet become full, and God granted them a period of probation before judgment. When that probation ended their destruction came, showing that God bears patiently with men but eventually brings judgment when they persist in rejecting light. Israel attained the full extent of these boundaries during David's reign, when the kingdom became a mighty nation. Beyond Canaan the promise points to its final fulfillment when the earth restored to Eden's beauty is given to Abraham as an everlasting possession.