I want to flag this for further consideration:
“Abraham was fully aware of the magical and idolatrous uses that could be developed from these mysteries. The Talmud thus says that Abraham had a tract dealing with idolatry that consisted of 400 chapters. There is also a Talmudic teaching that Abraham taught the mysteries involving ‘unclean names’ to the children of his concubines. This is based on the verse, ‘to the sons of the concubines that Abraham had, Abraham gave gifts, and he sent them away…to the lands of the east’ (Genesis 25:6). These gifts consisted of occult mysteries, which then spread in eastern Asia.”— Aryeh Kaplan, Sefer Yetzirah: The Book of Creation in Theory and Practice (xiii–xiv)
This, combined with Kaplan’s observation that the work of creation ought to be undertaken by a pair of men, places this tale of origins alongside the rich vein of Tamar stories that I spoke about previously.
I would be inclined to read this Talmudic account as something of an obfuscation, concealing the derivation of these practices from a Babylonian context. That doesn’t vitiate the core point—that there is Judaic form of this practice that necessarily excludes a family of operations alien to it.
It does indicate that there is a complementary non-Judaic form of the work and that non-Judaic practice is invoked under the rubric of four (400).
That the concubine will appear again and again in the accounts of how the Jewish people become a nation indicates that while the concubine must be excluded from the Jewish people, she must return again and again for their regeneration. Consider, too, that Isaiah specifies that the concubine will work for Israel in the Messianic work.