Shalom Halachicly a descendant of a convert to another religion remains Jewish, and it doesn’t end. However, I have had an opinion quoted to me that based on Shmot chapter 20 v5, the 4th generation would have to undergo a conversion. Where is this view found in the halachic literature and is it considered the halachah l’maasei? Todah
כ"ח טבת תשע"א I received your question not long ago. I apologize if there have been delays. The Rema (בשולחן ערוך יורה דעה סימן רסח סעיף יב) says that a "mumar" who has done Teshuva, although according to Torah law his repentance is sufficient, he is required by Rabbinical law to do tevila and announce in front of 3 people that he will never return to his rebellious ways. This is the Halacha long before the situation has reached a 4th generation. Contemporary poskim have explained that this requirement is only in a case in which a foreign faith was embraced and that no additional hurdles are placed in his way upon his return to his true faith. שו"ת ציץ אליעזר חלק יג סימן צג) , שו"ת מנחת יצחק חלק א' סימן י. However see also שו"ת מלמד להועיל חלק ב יו"ד סימן פד) If this is a practical question and not theoretical, then of course your local Dayan must be consulted.