John Gill Commentary Leviticus 18:19

"And thou shalt not approach unto a woman to uncover her nakedness, as long as she is impure by her uncleanness." — Leviticus 18:19 (ASV)

Also you shall not approach unto a woman
Not even a man to his own wife, and much less to another woman: to uncover her nakedness, as long as she is put apart for her
uncleanness ;
in her monthly courses; and the time of her separation from her husband on that account was seven days, (Leviticus 15:19) ; if a man lay with a woman when in such circumstances, they were both to be cut off from their people, (Leviticus 20:18) ; and such an action is reckoned among sins, and uncleanness of the worst sort, (Ezekiel 22:10) .