Vayikra 18:17-19

Orthodox Jewish Bible

¹⁷ Thou shalt not uncover the nakedness of an isha and her bat, neither shalt thou take the bat of her ben, or the bat of her bat, to uncover her nakedness; for they are her near kinswomen: it is zimmah (wickedness).

¹⁸ Neither shalt thou take your wife’s achot (sister), to be a rival wife, to uncover her nakedness, beside the other in her lifetime.

¹⁹ Also thou shalt not approach unto an isha to uncover her nakedness, as long as she has her tumah from her period of niddah.