Commentaire sur Chroniques 1 2:35

And Sheshan gave his daughter to Jarha his slave for a wife From here they derived that if your daughter has matured, free your slave and give him to her (Pes. 113a), and from here the Sages derived in the Palestinian Talmud, Tractate Yebamoth (source unknown): “Do not trust a proselyte until fifteen generations, and fifteen generations are from Ittai the Egyptian until Ishmael, and some say sixteen generations, including Jarha.” The midrash states the following: “Is it possible that he was of the royal descent (מִזֶּרַע הַמְלוּכָה) [as in Jeremiah 41:1]? Now was not Ishmael of the seed of Jerahmeel and not from Ram? But rather it means that he passed his seed to the molech.”