1,429. The Secondary Relationships; Issurei Lavin

Hilchos Ishus 1:6

There are some women with whom a man may not have relations by rabbinic enactment. These women are called “shniyos” (secondary relationships). There are 20 of these: (1) a person’s maternal grandmother, including her maternal grandmother and her maternal grandmother, etc.; (2) the mother of one’s maternal grandfather*; (3) one’s paternal grandmother, including the paternal grandmother’s maternal grandmother, etc.; (4) the mother of one’s paternal grandfather; (5) the wife of one’s paternal grandfather, continuing back up the line without interruption; the wife of our forefather Yaakov is prohibited to all of us; (6) the wife of one’s maternal grandfather; (7) the wife of one’s father’s brother from the same mother; (8) the wife of one’s mother’s brother, from either the same father or the same mother; (9) the daughter-in-law of one’s son, continuing down the line without interruption; all of our wives would be prohibited to our forefather Yaakov; (10) the daughter-in-law of one’s daughter; (11) the daughter of one’s son’s daughter; (12) the daughter of one’s son’s son; (13) the daughter of one’s daughter’s daughter; (14) the daughter of one’s daughter’s son; (15) the daughter of the son of one’s wife’s son; (16) the daughter of the daughter of one's wife’s daughter; (17) the maternal grandmother of one’s wife’s father; (18) the paternal grandmother of one's wife’s mother; (19) the maternal grandmother of one's wife’s mother; (20) the paternal grandmother of one’s wife’s father. There are four secondary relationships that go up or down the line without interruption: one’s maternal grandmother, paternal grandmother, and the wife of one’s paternal grandfather go up the line (i.e., to their ancestors) without interruption; the wife of one’s son’s son goes down the line (i.e., to descendants) without interruption.

*The Rambam actively indicates each time a relationship is limited to the person named; here, we only specify those relationship that go up or down a line. All the other secondary relationships are by default limited to the person named.

Hilchos Ishus 1:7

The Torah prohibits engaging in intimate relations with some people but engaging in relations with one of these people does not make one liable to the penalty of kareis (spiritual excision). These are called “issurei lavin” or “issurei kedusha.” There are nine such prohibited relationships: (1) between a widow and a Kohein Gadol; (2) between a divorcee, (3) a zonah** or (4) a chalalah# and a Kohein Gadol or a regular kohein; (5) between a mamzer† and a born Jew (as opposed to a convert); (6) between a born-Jewish woman and a convert from Moav or Ammon; (7) between a man and his ex-wife once she has married someone else in the interim; (8) between a born-Jewish woman and a man with crushed testes or a severed male member; (9) between a widow awaiting yibum (levirate marriage) and any man other than one of her husband’s brothers. By rabbinic enactment, a woman who has performed chalitzah (to be released from levirate marriage) is treated like a divorcee and is also prohibited to a kohein. The Sages also placed the Gibeonites in the same category as mamzeirim. The Gibeonites will be explained IY”H in Hilchos Issurei Biah (halachos 12:22-23 – see also Joshua chapter 9).

** Oversimplified, a woman who had intimate relations with a prohibited relationship. # A woman who has some aspect of Priestly affiliation but also some disqualifying aspect, such as the daughter of a kohein with a forbidden relationship. † The product of an adulterous or incestuous relationship.