For his sister, either by father or mother. Nigh unto him, i.e. by nearness, not of relation, (for that might seem a needless addition,) but of habitation, i.e. one not yet cut off from the family, as it follows. Which hath had no husband; for if she was married, she was now of another family, and under her husband's special care in those matters.
Related Commentaries of Leviticus 21:3
Leviticus 21:3
3 And for his sister a virgin, that is nigh unto him, which hath had no husband; for her may he be defiled.