Romans 4:17 (As it is written, I have made thee a father of many nations,) before him whom he believed, even God, who quickeneth the dead (corpses), and calleth those things which be not as though they were.
This verse tells us that the nature of our God is to call forth the things, which are still not physically in existence as having the same reality and essence of things, which are in existence.
This is one of the facets of faith!
Abraham’s faith in God was so great, that out of corpse like circumstances, and out of things, which in reality dis not exist, God made Abraham into a father of many nations and millions of people.
This is called the faith of Abraham.