A person does not render [unsealed objects in the room] ritually impure until his life departs. Even if he is lacerated, or terminal, [his legal status remains alive, and] he can obligate for yibum or release from yibum, and entitle [a relative] to eat terumah, or disqualify her from eating terumah. And so too wild and domesticated animals do not render objects impure until their life departs. Once they are decapitated, even though they still quiver, they are [immediately] impure; it is like the [severed] tail of a newt that quivers [without being alive].
The laws of ritual purity are an extremely complex topic in Judaism. When a person dies, objects in the room (or ohel, meaning tent) are rendered tamei, impure. Determining this consequence requires the rabbis to clarify the precise moment of death. Even a grievously injured person is considered legally alive until his life departs. Death is usually equated with the cessation of respiration. Until that point, even a terminally ill person continues to affect the legal status of others. Yibum is the obligation of a man to marry the widow of his childless brother. Terumah refers to tithes given to the priest and his family by Israelite farmers. While this man is alive, his sister-in-law is linked to him by the law of yibum, and, if he is a kohen, his widowed Israelite mother is still entitled to eat terumah. The postscript indicates that death is determined not by the cessation of movement, but by respiratory arrest or decapitation. This text supports the halakhic status of brain death (as argued in my responsum, “Contemporary Criteria for the Declaration of Death”).