Vayikra 18:18-20 Orthodox Jewish Bible (OJB)
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.
20 Moreover thou shalt not lie carnally with thy neighbor’s wife. You shall not give your shikhvat zera to make tamei with her.