The proselyte is regarded as a new-born child; hence his former family connections are considered as ended, and he might legally marry his own mother or sister; but lest he come to the conclusion that his new status is less holy than his former, such unions are prohibited (see Shulḥan 'Aruk, Yoreh De'ah, 269; "Yad," Issure Biah, xiv. 13). This conception of the proselyte's new birth (Yeb. 62a; Yer. Yeb. 4a) and of his new status with reference to his old family is the subject of many a halakie discussion (Yeb. xi. 2; Yer. Yeb. l.c.; et al.) and has led to certain regulations concerning marriages contracted either before or after conversion ("Yad," l.c. xiv. 13 et seq.; with reference to the first-fruit offering see Yer. Bik. 64a; Tosef., Bik. i. 2). That many of the earlier rabbis were opposed to proselytes is plain from observations imputed to them. R. Eliezer is credited with the opinion that the nature of proselytes is corrupt, and that hence they are apt to become backsliders (Mek., Mishpaṭim, 18; B. Ḳ. 59b; Gerim iv.). Jose ben Judah insists that any candidate should be rejected unless he binds himself to observe not only every tittle of the Torah but all the precepts of the scribes, even to the least of them (Tosef., Dem. ii. 5; Sifra 91a, to Lev. xix. 34).

According to R. Simeon b. Laḳish, proselytes are more precious at Sinai than Israel was, for the latter would not have taken the "kingdom" upon himself had not miracles accompanied revelation, while the former assume the "kingdom" without having seen even one miracle. Hence an injury to a proselyte is tantamount to an injury to G-d (Tan., Lek Leka, beginning; Ḥag. 5a). The proselyte might marry without restriction ("Yad," Issure Biah, xii. 17). The descendants of Ammon, Moab, Egypt, and [[Edom]] formed an exception: the males of Ammon and Moab were excluded forever, though no restriction existed against marriage with their women. Descendants of Egyptians and [[Edomites]] of either sex were proscribed in the first and second generations; the third enjoyed full connubial rights. But these restrictions were assumed to have been rendered inoperative by Sennacherib's conquest, and therefore as having no authority in later times ("Yad," l.c. xii. 17-24).

Besides the proselytes already mentioned, all belonging to the Roman period, there are records of others later. Among these were the kings of the Jewish Himyarite empire; Arab tribes (before the 6th cent.); Dhu Nuwas; Ḥarith ibn 'Amr; the Kenites; Waraḳah ibn-Naufal; the Chazars. Many also must have come from the ranks of the Christians; this would be the natural inference from the prohibition of conversion to Judaism issued by the Councils of Orleans, repeating previous prohibitions by Emperor Constantine. The code of Alfonso X. made conversion to Judaism a capital crime (Graetz, "Hist." ii. 562; iii. 37, 595).