Leviticus 18:18-20 Tree of Life Version (TLV)
18 You are not to marry your wife’s sister, to be a rival, uncovering her nakedness, while her sister is still alive.
Other Forbidden Relations
19 “You are not to approach a woman to uncover her nakedness while she is in the impurity of her niddah. 20 You are not to lie sexually with your neighbor’s wife and defile yourself with her.