וַיִּשָּׂ֨א יַעֲקֹ֜ב עֵינָ֗יו וַיַּרְא֙ וְהִנֵּ֣ה עֵשָׂ֣ו בָּ֔א וְעִמּ֕וֹ אַרְבַּ֥ע מֵא֖וֹת אִ֑ישׁ וַיַּ֣חַץ אֶת־הַיְלָדִ֗ים עַל־לֵאָה֙ וְעַל־רָחֵ֔ל וְעַ֖ל שְׁתֵּ֥י הַשְּׁפָחֽוֹת׃
And Jacob lifted up his eyes and looked, and, behold, Esau came, and with him four hundred men. And he divided the children unto Leah, and unto Rachel, and unto the two handmaids.
Zohar
The seventh precept is to perform circumcision on the eighth day of life and remove the defilement of the foreskin. Because that living creature is the eighth grade, compared to the other grades. And that soul that flies away and emerges from it must appear before it on the eighth day, as it in itself is the eighth grade.