Abraham is one of my favorite characters out of the Old Testament. The accounts of Abraham's life in Genesis are pretty amazing, although he also had some classic failures. But to me the most amazing aspect of Abraham's life is what is happening when we are first introduced to him.
The Biblical account of Abraham's life starts in the eleventh chapter of Genesis where we see Terah, his son Abram (later renamed to Abraham), Abram's wife Sarai (later renamed to Sarah), and his grandson Lot leave Ur of the Chaldeans to go to Canaan. It seems like Nahor, another son of Terah, also moved with them, at least part way. But along the way they stop and settle down in Haran for at least a while. While in Haran, Terah dies and God calls Abram to leave his family behind and continue the journey. So Abram, Sarai and Lot leave Haran and head for Canaan.
The rest of the account of Abraham in Genesis includes God's promises to Abraham concerning land and descendants, a journey to Egypt, the affair with Hagar and Ishmael, the rescue of Lot, the destruction of Sodom and Gomorrah, the birth of Isaac, the near sacrifice of Isaac and finding a wife for Isaac. Abraham is recorded as living in Canaan for 100 years. And in spite of several notable failures, he is commended as one who exhibited faith in God and becomes a primary example for faith by the author of Hebrews and by Paul in the letter to the Romans.
But why Abraham? Why did God choose to call him, out of all the other people who lived during that period of time? I find it doubtful that God just randomly chose him from among all the people who lived at that time. I find it much more likely that God chose Abraham because he knew how Abraham would respond to him.
Abraham is said to be from the city of Ur in Mesopotamia, a center of worship for the moon god Nannna. Was Abraham following Nanna when he received God's call? Or had he rejected Nanna to search for the God he saw revealed in the creation? In Romans 1:18-20, Paul claims that God's eternal nature and divine power are clearly seen in his creation and then goes on from there to claim that we have rejected that revelation and turned instead to gods of our own making, resulting in God turning us loose to our own devices. Because of that, I think it likely that Abraham was the rare exception who went the other way, rejecting man made gods and turning to seek the God revealed in creation. And God rewarded that seeking by making himself known to Abraham.
Ur was a major urban center, and while it is not possible to know with any certainty just what place Nahor's family had there, it is likely that they were free citizens and probably well off since they were free to uproot and move. Leaving Ur, and later Haran, behind to set off into the unknown would be a major challenge for me, and it is hard to imagine that it was easy for Abram when God called him to do so. But in some way Abram heard God's call, recognized it for what it was, and followed him from the comforts of city life into a life of wandering in the wilderness. Quite a chance, and yet no indication that Abraham ever had any serious doubts about following where God led.
Later on it is said of Abraham that he believed God, and God credited it to him as righteousness. Abraham's belief in God went beyond an intellectual acknowledgement of God existence. If it had we would never have heard of Abraham. Instead his belief amounted to obedience. When God told him something, he acted on it. And because of that, Abraham was consider to be righteous before God. Is it any different for us today?