Ohalos 1:2-3

Ohalos 1:2

The case of three being rendered impure is that utensils touch a corpse. Other utensils touching these utensils are rendered unclean with seven-day impurity. The third in this sequence, whether a person or more utensils, is unclean with impurity that lasts until nightfall.

Ohalos 1:3

The case of four being rendered impure is that utensils touch a corpse. A person touching these utensils and other utensils touching this person are rendered unclean with seven-day impurity. The fourth in this sequence, whether a person or more utensils, is unclean with impurity that lasts until nightfall. Rabbi Akiva proposed a case with a fifth stage: if a peg was fixed in a tent, then the tent, the peg, a person touching the peg and utensils touching the person are unclean with seven-day impurity. The fifth in this sequence, whether a person or more utensils, is unclean with impurity that lasts until nightfall. The Sages replied to Rabbi Akiva that tent the doesn't count (i.e., it is the corpse that conveys impurity inside a tent, not the tent itself).