And Terach Stayed in Harran

Now this is the line of Terah: Terah begot Abram, Nahor, and Haran; and Haran begot Lot. Haran died in the lifetime of his father Terah, in his native land, Ur of the Chaldeans... Terah took his son Abram, his grandson Lot the son of Haran, and his daughter-in-law Sarai, the wife of his son Abram, and they set out together from Ur of the Chaldeans for the land of Canaan; but when they had come as far as Haran, they settled there. The days of Terah came to 205 years; and Terah died in Haran.

During the times of Enosh, mankind made a great mistake, and the wise men of that generation gave thoughtless counsel. Enosh himself was one of those who erred.
Their mistake was as follows: They said God created stars and spheres with which to control the world. He placed them on high and treated them with honor, making them servants who minister before Him. Accordingly, it is fitting to praise and glorify them and to treat them with honor. [They perceived] this to be the will of God, blessed be He, that they magnify and honor those whom He magnified and honored, just as a king desires that the servants who stand before him be honored...

After many years passed, there arose people - false prophets - who told [their nations] that God had commanded them to say: Serve this star - or all the stars - sacrifice to it, offer libations to it, build a temple for it and make an image of it so that all people - including the women, the children, and the common people - could bow to it.

The world continued in this fashion until the pillar of the world - the Patriarch Abraham - was born. After this mighty man was weaned, he began to explore and think. Though he was a child, he began to think [incessantly] throughout the day and night, wondering: How is it possible for the sphere to continue to revolve without having anyone controlling it? Who is causing it to revolve? Surely, it does not cause itself to revolve.
He had no teacher, nor was there anyone to inform him. Rather, he was mired in Ur Kasdim among the foolish idolaters. His father, mother, and all the people [around him] were idol worshipers, and he would worship with them. [However,] his heart was exploring and [gaining] understanding.
Ultimately, he appreciated the way of truth and understood the path of righteousness through his accurate comprehension. He realized that there was one God who controlled the sphere, that He created everything, and that there is no other God among all the other entities. He knew that the entire world was making a mistake. What caused them to err was their service of the stars and images, which made them lose awareness of the truth.
Abraham was forty years old when he became aware of his Creator. When he recognized and knew Him, he began to formulate replies to the inhabitants of Ur Kasdim and debate with them, telling them that they were not following a proper path.
He broke their idols and began to teach the people that it is fitting to serve only the God of the world. To Him [alone] is it fitting to bow down, sacrifice, and offer libations, so that the people of future [generations] would recognize Him. [Conversely,] it is fitting to destroy and break all the images, lest all the people err concerning them, like those people who thought that there are no other gods besides these [images].
When he overcame them through the strength of his arguments, the king desired to kill him. He was [saved through] a miracle and left for Charan. [There,] he began to call in a loud voice to all people and inform them that there is one God in the entire world and it is proper to serve Him. He would go out and call to the people, gathering them in city after city and country after country, until he came to the land of Canaan - proclaiming [God's existence the entire time] - as [Genesis 21:33] states: "And He called there in the name of the Lord, the eternal God."

And when Abraham was forty years old etc. There is an Agadah (folktale) that he was three years old, as it is said: 'Because that Abraham hearkened unto My voice' (Gen. 26.5.). Hebrew for "Because" is 'EKB, which in numerals represent 172. Thus God says: 'EKB, or 172 years, that Abraham hearkened unto My voice. Abraham lived 175 years; deducting the three years before he recognized God, leaves 172.