• Decay of a corpse or detached parts as source of ritual impurity
• How much of a dead rodent is capable of causing ritual impurity
• How much of a corpse does contact with it compel a nazir to interrupt his nezirut
• Whether parts of two bodies combine to form the amount of ground-up bones from a corpse needed to cause impurity of a nazir
• The sources of impurity which do not cause a nazir to interrupt his nezirut
• The ritual impurity of entering land outside Eretz Yisrael
• The nazir afflicted with leprosy
• Entering the Sanctuary in a state of ritual impurity
• Doubt arising which of two nezirim became ritually impure
• Forbidden haircutting of a minor

• Nazir 51a

When one comes into contact with a human corpse he becomes ritually impure, even if the contact is with only a portion of the corpse. The exceptions to this rule are the teeth, hair and fingernails and toenails that have become detached from the corpse.

The rule regarding teeth helps explain what Rabbi Yochanan did when he went to comfort mourners. In order to express his empathy with their grief he pulled out of his pocket a small object that he said was a remnant of the tenth son he had buried in his lifetime.

Rashi (Berachot 5b) understood this object to be a bone, but of so tiny a size that it did not cause one to become ritually impure. The Sefer Aruch, however, defines the object as a tooth which, once detached from the corpse, no longer causes such impurity.

• The gemara's description of the long fasting of Rabbi Shimon in penitence for speaking irreverently about his departed master Rabbi Akiva