It was Abram' Faith coupled with contrition that allowed him the imputed righteousness of God. Babylon had no benchmark of God's will and plan that was still considered. The law of Hammurabi was the only righteous edict and it was far removed from the state of Abram's Ur.

But God call him out and imputed righteousness to restore a relationship.

Abram believed in the supreme, living, God. And heard the command to leave, seperate himself, and he did. The beginning works of repentance.