What was Abraham's argument in Genesis 15:2?
Abraham argued that God's covenant promises seemed unfulfilled because he remained childless. He had no seed or child; the steward of his house was Eliezer of Damascus, not a blood descendant, and one born in his house—Lot—was his heir, though Lot could never meet the criteria.
The teaching explains that Abraham understood and was not ignorant when God spoke to him in Ur, probably around age 50. God had promised a nation of people from his loins, yet Abraham asked how that could happen when he did not even have a first son. In Genesis 15:2 he said, "What wilt thou give me" regarding the covenant promises, seeing he went childless and the steward of his house was Eliezer of Damascus. Eliezer had no gene connection with Abraham; he was a hired servant. In verse 3 Abraham added that God had given him no seed, no child, and that one born in his house was his heir. The context identifies that one as Lot, who would never have filled the criteria.
And Abram said, LORD God, what wilt thou give me, seeing I go childless, and the steward of my house is this Eliezer of Damascus?