Wherever Jacob resided he studied the law as his fathers did. How is this, seeing the law had not yet been given, it is nevertheless written of Abraham (Gen. xxvi. 5), "And he kept my charge"? Whence then did Abraham learn the law? Rabbi Shimon says his reins (literally kidneys) were made like two water-jars, from which the law flowed forth. Where do we learn that it was so? From what is said in Ps. xvi. 7, "My reins also instruct me in the night season."
Bereshith Rabba, chap. 95.
The masters of the Kabbalah, of blessed memory, say that Abraham's Rabbi, i.e., teacher, was the angel Zadkiel.
Rabbi Menachem's comment on the Pent., Exod. iii. 5.
Adam's book, which contained celestial mysteries and holy wisdom, came down as an heirloom into the hands of Abraham, and he by means of it was able to see the glory of his Lord.
Zohar Parashah Bereshith.
Abraham was the author of a treatise on the subject of different kinds of witchcraft and its unholy workings and fruits, as also of the Book of Creation, through holy names (by means of which, namely, anything could be created).
Nishmath Chayim, chap. 29.
The whole world once believed that the souls of men were perishable, and that man had no pre-eminence above a beast, till Abraham came and preached the doctrine of immortality and transmigration.
Ibid., fol. 171, col. 1.