Since God gave Noah the responsibility of saving his family as well as the animals and to also then be fruitful and multiply, after He decided that the people He created were ‘evil’, then why does the bible refer to Abraham instead of Noah to be the ‘father of all nations’?
In Genesis chapter 17 God Covenants with Abraham that he will be the father of many nations. There is an important distinction that should be made though. The promise was a genealogical promise it was a spiritual promise, a promise of salvation. Genealogically, Abraham was the father of three distinct people groups through his two sons Ishmael and Isaac. Ishamael was his first born but he was the son of his wife’s servant Hagar, Ishmael’s descendants were the Ismaelites. Isaac was the son of his wife Sarah. From Isaac’s first born son Esau would come the Edomites, and from his other son Jacob (later named Israel) would come the nation of Israel from whom would come Jesus the savior. It is the later that is most significant when considering the Covenant with Abraham.
While all people are descended from Noah by blood, the significance of God’s Covenant with Abraham (that he would be Father of Many Nations) is not a promise of blood relation, it is a promise that all people would be blessed through him (Genesis 12). Ultimately that blessing would come through his descendent, Jesus Christ. Abraham is the father of many nations because all nations have access to Jesus, and can be heirs of Abraham’s blessing. This is a huge part of the Apostle Paul’s teaching in letters like Galatians and Romans.
God chose Abraham not Noah to be the line through whom the blessing would come. Why? All we know is that Abraham believed God when God promised him that he would be a Father of Many Nations. That’s no small thing, especially considering that Abraham and his wife Sarah could not bear children. In Genesis 15 it says, “Abraham believed God, and God credited to him as righteousness.” Like anyone else, Abraham wasn’t perfect, he made big mistakes, but he put his faith in God and His promise.