Leviticus 21:1-3

New Revised Standard Version, Anglicised Catholic Edition

The Holiness of Priests

21 The Lord said to Moses: Speak to the priests, the sons of Aaron, and say to them:

No one shall defile himself for a dead person among his relatives, ² except for his nearest kin: his mother, his father, his son, his daughter, his brother; ³ likewise, for a virgin sister, close to him because she has had no husband, he may defile himself for her.