Charles Spurgeon Commentary Romans 4:17

"(as it is written, A father of many nations have I made thee) before him whom he believed, [even] God, who giveth life to the dead, and calleth the things that are not, as though they were." — Romans 4:17 (ASV)

Before him whom he believed, even God, who gives life to the dead, and calls those things which are not as though they were.

Abraham was a believer in the God of resurrection, expecting to see Isaac raised up from the dead if he did actually offer him as a sacrifice to God. He was a believer in things that were not yet apparent to him, looking forward to them, and expecting to see them in due time; believing in them because he believed in God, who calls those things which are not as though they were.