Baruch S. Davidson: In Genesis 25:1-6, Abraham married a woman named Keturah and fathered six children. Abraham sent off the children whom she bore "eastward, to the Land of the East." They and their descendents are therefore not bound by the commandments of the Torah, which was given solely to the Jewish people, Isaac’s progeny. The only command that was given to Abraham and his children was circumcision.
Dov Krulwich: If Isaac was given "everything," what were the "gifts" given to the children of Ketura? Rashi explains as follows: "Our Rabbis explained, he gave them a name of God (meaning a Divine incantation) for impure uses." Commentaries on the Talmud explain this "name of God for impure uses" as "secrets of magic and powers of demons." The Daas Zekeinim explains this as "names of demons that are enlisted to do whatever their masters say." The Maharasha’s commentary on the Talmud says that Abraham learned black magic only to be able to defend against it, not to use it. Similarly, the Maharal says that Abraham taught these secrets to the children of Ketura only for defense (making Abraham perhaps the first teacher of defense against the dark arts). Whatever books the Zohar is referring to, we see the Talmud and Zohar presenting a consistent connection between Jewish teachings and Eastern mysticism, brought east by the children of Ketura. While some commentaries indicate that "The land to the east" might be areas just to the East of the Land of Israel, most understand this to be referring to the Far East.
Zohar VaYeira, paragraphs 80-89, Torah Shleima English Edition on Gen 25:6: Rabbi Abba said: I once was in a town where the children of the east live, and they taught me some of their ancient wisdom and showed me their books of wisdom…. I said to them, my children, all of this is similar to what we have in our Torah, but you should avoid these books, to avoid idolatry…. The ancient children of the east possessed a wisdom which they had inherited from Abraham, who had imparted it to the children of his other wife…
