After the Flood, it was the responsibility of Noah and his sons to share God’s will with their descendants. Noah’s family knew that global destruction had come to the world as a result of humanity’s refusal to obey God’s law and, having experienced God’s grace, they could do something to help develop a more faithful generation. Unfortunately, not too long after the Flood, the inhabitants of the earth again rebelled (Gen. 11:1-9). Many of them denied the existence of God and attributed the Flood to the operation of natural causes. Others believed in a Supreme Being, and that it was He who had destroyed the antediluvian world; and their hearts, like that of Cain, rose up in rebellion against Him.-Ellen G. White, Patriarchs and Prophets, p. 119.
God called Abraham, a descendant of Shem, and made a covenant of blessing with him (Gen. 12:1-3). The Bible gives no criteria for God’s call of Abraham. He does not appear to have had the righteous profile of Noah. In fact, soon after the call he proved himself to be cowardly and deceptive (Gen. 12:11-13), violating God’s law. Nevertheless, Abraham was a man of true faith, and by God’s grace this faith was credited to him as righteousness. Although he was not perfect, he was willing to listen to the voice of God, even if it meant trusting God for things that seem all but impossible from a human standpoint.
Abraham was not alone among those who were willing to listen to God’s voice and obey His commandments. Pharaoh, the two Abimelechs, and Joseph were well aware that God did not approve of adultery and lying. The second Abimelech even rebuked Isaac for exposing Abimelech’s people to temptation (Gen. 26:10). Although God had chosen Abraham for a specific task, there were people in many different nations who feared Him. In fact, after Abraham and his military alliance had defeated Chedorlaomer and his coalition, Abraham was blessed by King Melchizedek, who was a priest of the Most High God (Gen. 14:18, TEV). This is more evidence that knowledge of God existed in the world at that time, even before the work and ministry of Moses.