'In Me' in the Bible

For certain men have secretly infiltrated [your ranks]; they are men who had been written about long ago that they should be judged [and condemned] for perverting the unearned favor of our God into [a license for] living unrestrained, indecent lives, and who deny [the identity and work of] our only Master and Lord, Jesus Christ.

But these people [i.e., the "certain men" of verse 4] speak against whatever they do not understand, and what they do understand naturally, the way animals do, proves to be their ruination.