Leviticus 21:1-3

1And Jehovah said to Moses, Speak unto the priests, the sons of Aaron, and say unto them, There shall none make himself unclean for a dead person among his peoples,

2except for his immediate relation, who is near unto him — for his mother, and for his father, and for his son, and for his daughter, and for his brother;

3and for his sister, a virgin, that is near unto him, who hath had no husband, for her may he make himself unclean.