Tertullian said that the Nicolaitans were gnostics that taught that there was nothing wrong with any kind of fornication or adultery. (This was a common teaching among some gnostics who, since they believed that matter and flesh were evil and that the soul was separate from the body, taught that there was no such thing as "sins of the flesh."
This notion survives in certain parts of the Church today.
A brother heretic21 emerged in Nicolaus. He was one of the seven deacons who were appointed in the Acts of the Apostles.22 He affirms that Darkness was seized with a concupiscenceand, indeed, a foul and obscene oneafter Light: out of this permixture it is a shame to say what fetid and unclean (combinations arose). The rest (of his tenets), too, are obscene. For he tells of certain eons, sons of turpitude, and of conjunctions of execrable and obscene embraces and per-mixtures,23 and certain yet baser outcomes of these. He teaches that there were born, moreover, dµmons, and gods, and spirits seven, and other things sufficiently sacrilegious. alike and foul, which we blush to recount, and at once pass them by. Enough it is for us that this heresy of the Nicolaitans has been condemned by the Apocalypse of the Lord with the weightiest authority attaching to a sentence, in saying "Because this thou holdest, thou hatest the doctrine of the Nicolaitans, which I too hate."24
Roberts, Alexander, James Donaldson and A. Cleveland Coxe. The Ante-Nicene Fathers Vol. III : Translations of the Writings of the Fathers Down to A.D. 325, p 650. Oak Harbor: Logos Research Systems, 1997.
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Nicolaitans (ni-koh-layʹi-tahns), a religious sect in Ephesus and Pergamum whose members were denounced in Rev. 2:6, 15 for eating food sacrificed to idols and for sexual license. The church fathers considered them followers of Nicolaus of Antioch mentioned in Acts 6:5 and founders of libertine Gnosticism, which remained active beyond the second century. Though this suggestion is possible, not many scholars would regard it as historically reliable. See also Revelation to John, The; Ephesus; Pergamum.
Achtemeier, Paul J., Publishers Harper & Row and Society of Biblical Literature.
Harper's Bible Dictionary. 1st ed., p 704. San Francisco: Harper & Row, 1985.