Rashi on Leviticus 20:12/רש"י על ויקרא כ׳:י״ב

1תבל עשו THEY HAVE WROUGHT תבל — i. e. they have done a shameful deed. Another interpretation is that תבל is connected with בלל to "intermingle" and signifies that they mingle (בּלל) the seed of the father with the seed of the son.