Imamat 18:11

18:11 You must not have sexual intercourse with the daughter of your father’s wife born of your father; she is your sister. You must not have intercourse with her. ¹ 

Imamat 20:17

20:17 “‘If a man has sexual intercourse with ²  his sister, whether the daughter of his father or his mother, so that he sees her nakedness and she sees his nakedness, it is a disgrace. They must be cut off in the sight of the children of their people. ³  He has exposed his sister’s nakedness; he will bear his punishment for iniquity. ⁴ 

Ulangan 27:22

27:22 ‘Cursed is the one who has sexual relations with his sister, the daughter of either his father or mother.’ Then all the people will say, ‘Amen!’

[18:11]  ¹ tn Heb “The nakedness of the daughter of your father’s wife born of your father, she is your sister; you must not uncover her nakedness.” That is, a half sister, the daughter of the man’s father by another wife, who is not the man’s mother, is to be considered a true sister. Therefore, the man must not have sexual intercourse with her.

[20:17]  ² tn Heb “takes.” The verb “to take” in this context means “to engage in sexual intercourse,” though some English versions translate it as “marry” (e.g., NIV, NCV, TEV, CEV).

[20:17]  ³ tn Regarding the “cut off” penalty, see the note on Lev 7:20.

[20:17]  ⁴ tn See the note on Lev 17:16 above.