In Rom. 4:12 the Apostle Paul declares that Abraham was the father, not of his physical offspring alone, but also of those who “walk in the steps of that faith” which Abraham had.
Have you ever noticed that God does not hold the great men of Scripture up to us because of their personal virtues? Almost invariably their records are marred by failure and sin. But God bids us to observe their faith and what their faith gained for them (See Rom. 4:3,9,11,12).
There is a whole chapter on this subject in the Book of Hebrews. Hebrews 11 is properly called “the great faith chapter,” and its heroes “heroes of faith,” for it tells how Abel, Enoch, Noah, Abraham, Isaac, Jacob and scores of others “obtained a good report” before God. They all faltered and failed again and again, but Heb. 11:39 declares that “these all… obtained a good report THROUGH FAITH.”
This is why Rom. 4:9-12 states that God’s blessing is bestowed upon those who “walk in the steps of that faith” which Abraham exhibited, just as it was bestowed upon Abraham himself.
This truth is driven home in Verses 3 to 5 of the same chapter:
“For what saith the Scripture? Abraham believed God, and it was counted unto him for righteousness. Now to him that worketh is the reward not reckoned of grace, but of debt. But to him that worketh not, but believeth on Him that justifieth the ungodly, his faith is counted for righteousness” (Rom. 4:3-5). source