brought to you by Kollel Iyun Hadaf of Yerushalayim
& Revach l'Neshamah - http://www.revach.net
1. A Zav and Ba'al Keri become Tamei only when their emission exits their bodies.
2. A Ba'al Keri who immersed in a Mikvah -- but did not urinate since the time before he became a Ba'al Keri -- becomes a Ba'al Keri again after he urinates.
3. The Gemara discusses the moment at which the status of Keri which eventually leaves the body is determined.
4. A man who has a Zav emission becomes a Zav after two such emissions, and he must bring a Korban after three.
5. The Mishnah lists many things that apply to a male child upon birth.
A BIT MORE
1. This is derived from the verse, "When it will flow from his flesh," implying that he is considered a Zav only when the emission actually exits his body. Similarly, regarding a Ba'al Keri the verse states, "And when a man will have Keri emitted from him."
2. This is because upon urinating he emits any remnants of Keri from when he became a Ba'al Keri, causing him to become Tamei again.
3. There is a dispute about whether the Keri's status is determined at the time a man starts to feel it leaving his body even though it has not yet left, or when it physically leaves his body. For example, in a case in which a Nochri felt Keri start to leave his body, he immersed in order to convert and become a Jew, and then the Keri actually left his body, the Gemara remains in doubt ("Teiku") about the status of his Keri.
4. There is a dispute about which source in the verse teaches this distinction.
5. For example, he can have a Zav emission which is Tamei, Tzara'as, and Tum'as Mes. He also can cause his childless dead brother's wife to require Chalitzah if he is born a day before his brother dies.
Next Daf Index to Revach for Maseches Nidah