A.T. Robertson Commentary 1 Thessalonians 5:22

"abstain from every form of evil." — 1 Thessalonians 5:22 (ASV)

Abstain from every form of evil (απο παντος ειδους πονηρου απεχεσθε). Present middle (direct) imperative of απ-εχω (contrast with κατ-εχω) and preposition απο repeated with ablative as in 1 Thessalonians 4:3. Note use of πονηρου here for evil without the article, common enough idiom. Ειδος (from ειδον) naturally means look or appearance as in Lu 3:23; 9:29; John 5:37; 2 Corinthians 5:7. But, if so taken, it is not semblance as opposed to reality (Milligan). The papyri give several examples of ειδος in the sense of class or kind and that idea suits best here. Evil had a way of showing itself even in the spiritual gifts including prophecy.