New Defender's Study Bible Notes
6:18 fornication. In Biblical usage, “fornication” can mean any sexual congress outside monogamous marriage. It thus includes not only premarital sex, but also adultery, homosexual acts, incest, remarriage after un-Biblical divorce, and sexual acts with animals, all of which are explicitly forbidden in the law as given through Moses (e.g., Leviticus 20:10-21). Christ expanded the prohibition against adultery to include even sexual lusting (Matthew 5:28).