Abram was commanded to leave his father's house because his father did what?

Answer 1

Answer #1: It was because his father (Terah) worshiped idols. This reason is stated explicitly in the Midrash on Genesis 12:1.

Abram (Abraham) came from ancestry that had been God-fearing a couple of centuries earlier but had afterwards slipped into idolatry (Joshua 24:2). Nimrod, the idolatrous tyrant, had brought Abram's father (Terah) from the Semitic ancestral seat in north Babylonia, and instated him in a position of power in his army in the royal Babylonian city of Ur, where Abram was born. Nimrod persecuted any who would question his idolatrous cult.

The Kuzari (Rabbi Judah HaLevi, 1075-1141) states that Abraham was gifted with high intelligence; and, as Maimonides (1135-1204) describes, Abram didn't blindly accept the ubiquitous idolatry, although the population at large did. The young Abram contemplated the matter relentlessly, finally arriving at the conclusion that there is One God and that this should be taught to others as well. This is what is meant by his "calling out in the name of the Lord" (Genesis ch.12). As a young man, he remonstrated with passersby in public, demonstrating to them the falsehood of their idols. Terah, however, remained an idolater, and God told Abram to leave him.

Answer #2: We know that Abraham descended from idol worshipers, and that he had been raised in his father's traditions from childhood . We know that at some point in his life, he was told to leave his father's home and his home town, and to hit the road. We know that he wasn't told any destination, and we know that he obeyed. Asking for a "because" is very near asking to understand the mind of God. This website can pull off some pretty nifty things sometimes, but that isn't one of them.