'Illicit' in the Bible

Furthermore, no one born due to an illicit sexual relationship may participate in the assembly of the LORD, including his descendants to the tenth generation.

Such is the way of all those who seek illicit gain it takes away the lives of those who possess it.

Then I said concerning this woman worn out by adultery: Will they now have illicit sex with her, even her?

You adulteresses [disloyal sinners—flirting with the world and breaking your vow to God]! Do you not know that being the world’s friend [that is, loving the things of the world] is being God’s enemy? So whoever chooses to be a friend of the world makes himself an enemy of God.