Abraham stepped out of the cave where he had been hidden as an infant, and for the first time saw the world above ground. He looked up and saw the sun climbing, enormous and warm, and he thought: surely this is God. He worshipped it. Then the sun set, and the moon rose, silver and calm, and he thought: the sun has a ruler too, and it is this. He worshipped the moon. Then the moon set, and the stars wheeled, and at last the true God spoke in the silence behind all of them: I am the Lord, and I made each of those lights. Abraham worshipped Him.
He returned to his father Terah's house, where the shelves were crowded with idols his father sold for profit. When Terah sent him to carry a sacrifice to the statues, Abraham watched the gods of wood and stone sit motionless before their portion. They could not so much as lift a crumb. Abraham set the whole house on fire and watched his father's merchandise burn.
Word traveled fast. Abraham was brought before Nimrod, the king who had declared himself a god. "If you are God," Abraham said evenly, "then make the sun rise in the west tomorrow and set in the east." Nimrod could not. In answer, he ordered a furnace heated and commanded that Abraham be thrown into it.
The king's magicians whispered that the fire would not hurt him because his brother Haran was an astrologer and a fire-worshipper, and that this family practiced spells. They were wrong. Abraham walked through the flames unburned because the God who made the sun held him in His hand. A single spark leapt out and struck Haran — who had not committed to any side with full heart — and burned him to death.
All the nations watching that day, the midrash says, recognized the superiority of the God of Abraham. The furnace that was meant to silence him became the first altar of his public witness.
(From The Exempla of the Rabbis, Moses Gaster, 1924, no. 2b, drawing on the Ma'aseh Book / Codex Gaster.)