Kiddushin 75B

ורבי ישמעאל סבר לה כרבי עקיבא. רבי אלעזר סבר לה כרבי ישמעאל, דאמר: כותים גירי אריות הם. ורבי ישמעאל סבר לה כרבי עקיבא, דאמר: נכרי ועבד הבא על בת ישראל ⁠– הולד ממזר.

and R' Yishmael holds in accordance with the opinion of R' Akiva concerning a different halakha. The Talmud clarifies: R' Elazar holds in accordance with the opinion of R' Yishmael, who says: Samaritans are lion converts, i.e., they converted out of fear of being attacked by lions for worshipping idols in Eretz Yisrael. They were never converts for the sake of Heaven, but remained non-Jews according to halakha. And R' Yishmael holds in accordance with the opinion of R' Akiva, who says: In the case of a non-Jew or a Canaanite slave who had sex with a Jewish woman, the offspring is a mamzer. Since over the generations Jews assimilated with Samaritans, who have the status of non-Jews, the descendants of those Jews who married Samaritans have the status of uncertain mamzerim.

ומי סבר לה רבי ישמעאל כרבי עקיבא? והאמר רבי יוחנן משום רבי ישמעאל: מנין לנכרי ועבד שבאו על הכהנת ועל הלויה ועל בת ישראל שפסלוה? שנאמר: ״ובת כהן כי תהיה אלמנה וגרושה וזרע אין לה״

The Talmud asks: But does R' Yishmael hold in accordance with the opinion of R' Akiva in this matter? But doesn’t R' Yoḥanan say in the name of R' Yishmael: From where is it derived with regard to a non-Jew or a Canaanite slave who had sex with the daughter of a priest, or with the daughter of a Levite, or with the daughter of an Israelite, that they have disqualified her from marrying a priest? It is as it is stated: “But if a priest’s daughter is a widow, or divorced, and has no child, and is returned to her father’s house, as in her youth, she may eat of her father’s bread” (Leviticus 22:13).