זוהר שמות — דף קט ע”א

Castration is forbidden in Israel and for livestock in the land of Israel because it constitutes a defect in the covenant and in the completeness of the divine form. The Hebrew slave whose wife was given to him by his master — his wife and children remain with the master upon his release. The Holy One assembles unions according to judgment: one who has merited receives a worthy companion, and one who has not merited receives according to his deeds.