18
You are not to marry a woman as a rival to her sister and have sexual intercourse with her during her [sister's] lifetime.
Leviticus 18:18 In-Context
16
“ ‘Do not have sexual relations with your brother’s wife; that would dishonor your brother.
17
“ ‘Do not have sexual relations with both a woman and her daughter. Do not have sexual relations with either her son’s daughter or her daughter’s daughter; they are her close relatives. That is wickedness.
18
“ ‘Do not take your wife’s sister as a rival wife and have sexual relations with her while your wife is living.
19
“ ‘Do not approach a woman to have sexual relations during the uncleanness of her monthly period.
20
“ ‘Do not have sexual relations with your neighbor’s wife and defile yourself with her.