Then the Shaykh (Al-Mufid), may Allah سبحانه وتعالى support him, said: "If it comes into contact with the carcass of something other than a human, it also renders the garment impure, and it must be washed with water." The principle here is that a dead body is impure without dispute. Therefore, if a garment comes into contact with impurity, it must be purified to ensure one enters prayer with certainty about the purity of the garment. This is also supported by (following hadith):
Commentary #33