Leviticus 18:15

18:15 You must not have sexual intercourse with your daughter-in-law; she is your son’s wife. You must not have intercourse with her.

Genesis 38:16

38:16 He turned aside to her along the road and said, “Come on! I want to have sex with you.” ¹  (He did not realize ²  it was his daughter-in-law.) She asked, “What will you give me in exchange for having sex with you?” ³ 

Genesis 38:18

38:18 He said, “What pledge should I give you?” She replied, “Your seal, your cord, and the staff that’s in your hand.” So he gave them to her and had sex with her. ⁴  She became pregnant by him.

Deuteronomy 27:23

27:23 ‘Cursed is the one who has sexual relations with his mother-in-law.’ Then all the people will say, ‘Amen!’

[38:16]  ¹ tn Heb “I will go to you.” The imperfect verbal form probably indicates his desire here. The expression “go to” is a euphemism for sexual intercourse.

[38:16]  ² tn Heb “for he did not know that.”

[38:16]  ³ tn Heb “when you come to me.” This expression is a euphemism for sexual intercourse.

[38:18]  ⁴ tn Heb “and he went to her.” This expression is a euphemism for sexual intercourse.