Bekhorot 47A

״יכיר״ לחוד, והכרת פנים לחוד.

The requirement of “He should recognize” with regard to a firstborn for inheritance, and the recognition of a husband’s face, are discrete matters.

איתמר: היו לו בנים בגיותו ונתגייר ⁠— רבי יוחנן אומר: אין לו בכור לנחלה, ורבי שמעון בן לקיש אומר: יש לו בכור לנחלה. רבי יוחנן אומר: אין לו בכור לנחלה ⁠— דהא הוה ליה ״ראשית אונו״, ורבי שמעון בן לקיש אומר: יש לו בכור לנחלה ⁠— גר שנתגייר כקטן שנולד דמי.

§ It was stated that amora’im engaged in a dispute concerning the case of a man who had children when he was a non-Jew and he subsequently converted: R' Yoḥanan says he does not have a firstborn with regard to inheritance, i.e., a son who is his firstborn after his conversion does not inherit a double portion; and R' Shimon ben Lakish says: He does have a firstborn with regard to inheritance. The Talmud elaborates: R' Yoḥanan says: He does not have a firstborn with regard to inheritance, as this man already had “the first of his strength” (Deuteronomy 21:17), the Torah’s description of the firstborn in this context, before he converted. And R' Shimon ben Lakish says: He does have a firstborn with regard to inheritance, as the halakhic status of a convert who just converted is like that of a child just born.

ואזדו לטעמייהו, דאיתמר: היו לו בנים בגיותו ונתגייר ⁠— רבי יוחנן אמר: קיים פריה ורביה, ורבי שמעון בן לקיש אמר: לא קיים. רבי יוחנן אמר: קיים ⁠— ״לא תהו בראה לשבת יצרה״, ורבי שמעון בן לקיש אמר: לא קיים פריה ורביה ⁠— גר שנתגייר כקטן שנולד דמי.

The Talmud comments: And these amora’im follow their regular line of reasoning, as it was stated: If a man had children when he was a non-Jew and he subsequently converted, R' Yoḥanan says: He has already fulfilled the mitzva to be fruitful and multiply, and R' Shimon ben Lakish says: He has not fulfilled the mitzva to be fruitful and multiply. The Talmud clarifies: R' Yoḥanan says he has fulfilled the aspect of the mitzva to be fruitful and multiply expressed in the command: “He did not create it to be a waste; He formed it to be inhabited” (Isaiah 45:18), i.e., to increase the inhabitation of the world. And R' Shimon ben Lakish says he has not fulfilled the mitzva to be fruitful and multiply, as the halakhic status of a convert who just converted is like that of a child just born, and it is considered as though he did not have children.