Why did God reach out to Abraham even though he was an idolater?
God reached out because He saw in Abraham the potential to believe what He said. Although Abraham lived in abject idolatry and had no knowledge of the One True God, God spoke to him and appeared to him, and he became the example of being justified by faith alone.
Les explains that Abraham was raised and living in abject idolatry and had no knowledge of the One True God. Yet God saw in that man the potential to believe what He said, so He reached down, spoke to him, and appeared to him in a physical form more than once, communicating with him. Paul, by inspiration, then goes back to Abraham as the perfect example of what it is to be justified—made totally righteous by faith, and faith alone, plus nothing. The promise that he should be heir of the world was not through the law, but through the righteousness of faith, because the law worketh wrath.