Leviticus 21:2

But for his kin, that is near unto him, that is, for his mother, and for his father, and for his son, and for his daughter, and for his brother,

Cross-reference

Leviticus 21:11 forbids the high priest from any corpse contact, even for parents — contrasting with the regular priest's allowance here.

Numbers 6:7 prohibits a Nazirite from defiling himself even for parents, contrasting with this permission for priests to mourn close kin.