Genesis 13:16
14 After Lot had departed, the Lord said to Abram, “Look from the place where you stand to the north, south, east, and west. 15 I will give all the land that you see to you and your descendants forever. 16 And I will make your descendants like the dust of the earth, so that if anyone is able to count the dust of the earth, then your descendants also can be counted. 17 Get up and walk throughout the land, for I will give it to you.” 18 So Abram moved his tents and went to live by the oaks of Mamre in Hebron, and he built an altar to the Lord there.
Numbers 23:10
8 How can I curse one whom God has not cursed, or how can I denounce one whom the Lord has not denounced? 9 For from the top of the rocks I see them; from the hills I watch them. Indeed, a nation that lives alone, and it will not be reckoned among the nations. 10 Who can count the dust of Jacob, or number the fourth part of Israel? Let me die the death of the upright, and let the end of my life be like theirs.” 11 Then Balak said to Balaam, “What have you done to me? I brought you to curse my enemies, but on the contrary you have only blessed them!” 12 Balaam replied, “Must I not be careful to speak what the Lord has put in my mouth?”
Notes and References
"... the promises that the land will belong to Abram‘s descendants for ever and that these descendants will be numberless as the dust of the earth look even further into the future. That the land will be Israel‘s everlasting possession is reaffirmed in 17:8; 48:4, and is the presupposition informing the jubilee year legislation and the inheritance laws (Leviticus 25:25–34; Numbers 36:5–9). The God-givenness of the land is a central theme of Deuteronomy (e.g., 3:18–21; 30:3–5) and the basis of the prophetic hope that Israel will return there after exile (e.g., Jeremiah 31:2–21). The uncountability of Abram‘s descendants is a perennial theme of Genesis: 15:5; 16:10; 28:14; 32:12. Balaam, the prophet hired by the king of Moab to curse Israel, said Israel was already beyond counting in his day (Numbers 23:10). Solomon said the same thing some centuries later (1 Kings 3:8), though of course both eras were famed for their censuses ..."
Wenham, Gordon J. Word Biblical Commentary: Genesis 1-15 (pp. 360-361) Word Books, 1987