These are fit in man but unfit in animals: A father and son, a tereifah, one delivered by Caesarean section, one with whom a sin has been committed, or one that has killed a person. One who marries forbidden women is unfit, until he pronounces a vow pro-hibiting him from deriving benefit [from them]. One who contaminates himself with [the tumah of] dead bodies is unfit, until he pledges not to contaminate himself with [the tumah of] dead bodies.