Leviticus 21:1, 11

Then the LORD said to Moses, “Speak to the priests, the sons of Aaron, and say to them: ‘ N o one shall defile himself [that is, become ceremonially unclean] for the dead among his people [by touching a corpse or assisting in preparing it for burial]

nor shall he approach any dead person, nor defile himself [by doing so, even] for his father or for his mother