Imamat 20:14

20:14 If a man has sexual intercourse with both a woman and her mother, ¹  it is lewdness. ²  Both he and they must be burned to death, ³  so there is no lewdness in your midst.

Ulangan 27:23

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

[20:14]  ¹ tn Heb “And a man who takes a woman and her mother.” The Hebrew verb “to take” in this context means “to engage in sexual intercourse.”

[20:14]  ² tn Regarding “lewdness,” see the note on Lev 18:17 above.

[20:14]  ³ tn Heb “in fire they shall burn him and them.” The active plural verb sometimes requires a passive translation (GKC 460 §144.f, g), esp. when no active plural subject has been expressed in the context. The present translation specifies “burned to death” because the traditional rendering “burnt with fire” (KJV, ASV; NASB “burned with fire”) could be understood to mean “branded” or otherwise burned, but not fatally.