Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[154] Now Abram, having no son of his own, adopted Lot, his brother Haran's son, and his wife Sarai's brother; and he left the land of Chaldea when he was seventy-five years old, and at the command of God went into Canaan, and therein he dwelt himself, and left it to his posterity. He was a person of great sagacity, both for understanding all things and persuading his hearers, and not mistaken in his opinions; for which reason he began to have higher notions of virtue than others had, and he determined to renew and to change the opinion all men happened then to have concerning God; for he was the first that ventured to publish this notion, That there was but one God, the Creator of the universe; and that, as to other [gods], if they contributed any thing to the happiness of men, that each of them afforded it only according to his appointment, and not by their own power. This his opinion was derived from the irregular phenomena that were visible both at land and sea, as well as those that happen to the sun, and moon, and all the heavenly bodies, thus: - "If [said he] these bodies had power of their own, they would certainly take care of their own regular motions; but since they do not preserve such regularity, they make it plain, that in so far as they co-operate to our advantage, they do it not of their own abilities, but as they are subservient to Him that commands them, to whom alone we ought justly to offer our honor and thanksgiving." For which doctrines, when the Chaldeans, and other people of Mesopotamia, raised a tumult against him, he thought fit to leave that country; and at the command and by the assistance of God, he came and lived in the land of Canaan. And when he was there settled, he built an altar, and performed a sacrifice to God.