וְאִ֗ישׁ אֲשֶׁ֤ר יִשְׁכַּב֙ אֶת־כַּלָּת֔וֹ מ֥וֹת יוּמְת֖וּ שְׁנֵיהֶ֑ם תֶּ֥בֶל עָשׂ֖וּ דְּמֵיהֶ֥ם בָּֽם׃
And if a man lie with his daughter-in-law, both of them shall surely be put to death; they have wrought corruption; their blood shall be upon them.
Read kabbalistic (mystical) interpretation of Leviticus 20:12: and classical mystical sources.