“Prove all things; hold fast that which is good.”
King James Version (KJV)
5:21 Meantime, prove all things - Which any preacher recommends. (He speaks of practice, not of doctrines.) Try every advice by the touchstone of scripture, and hold fast that which is good - Zealously, resolutely, diligently practise it, in spite of all opposition.
1Th 5:21 Prove all things. What was spoken they must put to the test, they must hold fast to. There were those who could "discern spirits" (1Co 12:10). There were also rules for testing (1Jo 4:1-8).