Just on the side, there is an important clue in today's text regarding the nature and extent of divine inspiration in the Bible you carry to church. Its in that 23rd verse - "But the words, 'it was counted to him...' " Paul focuses his whole interpretation on the words he quotes from the Old Testament regarding the faith of Abraham. His whole argument requires the accuracy of nouns and verbs. He places his complete trust in them. That's important to remember.
The Apostle Paul goes on to explain that Abraham's faith - faith exercised when there was yet no Israel or Jewish religion - Abraham's faith exercised while he was still a Gentile - this faith serves as a root and pattern for God's redeeming gift of righteousness for all people, including you and me, through faith. This is what Paul means in those bold words in verses 23-24 - "But the words 'it was counted to him' were not written for his sake alone, ...but for ours also. It will be counted to us who believe in him who raised from the dead Jesus our Lord...."