(Mishnah): Beis Din can warn the wife of a man that became deaf, or insane, or was imprisoned;

This is not to be Mashkeh her, rather, to forfeit her Kesuvah [if she will be secluded].

R. Yosi says, it is even to be Mashkeh her. When her husband is released from jail, he can make her drink.

(Gemara): [We learn that Beis Din can be Mekanei from] "Bnei Yisrael... v'Kinei."

Question: [If so, Beis Din] should be Mashkeh her!

Answer: It is a Gezeiras ha'Kasuv "v'Hevi ha'Ish Es Ishto El ha'Kohen." (Above (18b), this taught that he is not Mashkeh an Arusah.)

Question: [If so, he] should not be Mekanei [an Arusah]!

Answer: The Torah said "v'Kinei Es Ishto... v'Kinei Es Ishto" - even his partial wife. (We explained this like HA'MASHBI'ACH.)

Question: What is the source that Bi'ah of Pesulim disqualifies?

If [you want to learn] from an Eshes Ish [you cannot], for she is stringent! (There is Kares, Misas Beis Din and the child is a Mamzer.) If from a widow to a Kohen Gadol [you cannot learn], for Pesulim of Kehunah are different!

Answer: The Tzad ha'Shavah of them - one whose seed [from this woman] is Pasul, his Bi'ah disqualifies [her].

The following [disqualify] - a male [at least] nine years old and one day, who is a converted Amoni, Mo'avi, Mitzri or Edomi, a slave, Mamzer, Chalal, Nasin, Kusi or Nochri, who had Bi'ah with a Bas Kohen, Bas Levi or Bas Yisrael, he disqualified her from Kehunah.

R. Yosi says, anyone whose seed is Pasul, his Bi'ah disqualifies. Anyone whose seed is not Pasul, his Bi'ah does not disqualify. (This excludes a Mitzri Sheni and Edomi Sheni; their children are Kesherim.)

R. Shimon ben Gamliel says, anyone that you (a Kohen) may marry his daughter, you may marry his widow (he did not disqualify her through Bi'ah). Anyone that you may not marry his daughter, you may not marry his widow. (This excludes also an Amoni u'Mo'avi; their daughters are Kesherim.)