John Gill's Exposition of the Whole Bible
Leviticus 21:3
And for his sister a virgin, that is nigh unto him,.... That is, his sister by both father's and mother's side, as Aben Ezra; though, according to Gersom, his sister by his father's side, and not by his mother's side, is meant; but, according to Alphes, by his mother's side: perhaps this may signify not nearness of kin, which is expressed by being his sister, but nearness of place, for, being unmarried, she remained unto her death in her father's house:
which hath had no husband; neither betrothed to one, for then she would have been nigh to her husband, and not her brother, and therefore he might not pollute himself for her, as Gersom observes; nor married to him, for such an one he might not defile himself, even though she might have been rejected or divorced by her husband, as the same writer says:
for her may he be defiled; for a pure virgin that had never been betrothed nor married to a man, and had never departed from her father's house, and so had no husband to mourn for her, and take care of her funeral, and so for all the rest before mentioned; and which Jarchi says is a command, and not a bare sufferance or allowance, but what he ought and was obliged to do; and so it is related of Joseph r, a priest, that his wife died in the evening of the sabbath, and he would not defile himself for her, and his brethren the priests obliged him, and made him defile himself against his will.
r T. Bab. Zebachim, fol. 90. 1.