A.W. Tozer addresses the concept of zeal in the Christian life, emphasizing that while true Christians should exhibit fervent zeal for God, it is possible to be zealous without being genuinely Christian. He critiques the notion that zeal alone is a marker of godliness, pointing out that many zealous individuals or groups, such as Jehovah's Witnesses and other religions, demonstrate fervor but are not aligned with biblical truth. Tozer warns that zeal must be accompanied by sound doctrine and a true relationship with Christ, as mere enthusiasm does not equate to righteousness. He highlights that even those with misguided zeal can be more fervent than true believers, underscoring the need for discernment in evaluating spiritual fervor.

Zeal, according to Webster, means ardor in the pursuit of anything; ardent and active interest; enthusiasm; fervor. Surely this should describe a Christian, and the better the Christian the more accurately it should apply. The devout soul should and will be fervent. He will pursue the things of God actively and be enthusiastic in his cultivation of the spiritual life. In his attitude toward Christ he will manifest fervid love and burning devotion. So we would seem to go along with the majority who hold zeal to be a sure mark of godliness. But it is only seeming. We do not go along with them, and here are the reasons: While the true Christian is zealous, it is altogether possible to be zealous and not be a Christian. Zeal proves only that the one who manifests it is healthy, energetic and actively interested in something. As far as my experience goes, the most zealous religionists of our day are the wrongly named Jehovah's Witnesses. If zeal indicates godliness, then these ardent devotees of error are saints of the first order, a notion that could hardly be entertained by anyone who knew them intimately. Next to them, in the degree of temperature they manage to generate over their religion, are the "Peace! It's wonderful" dupes of the little dark, lower-case god, Father Divine. They are ablaze with zeal, but they are nevertheless condemned on every page of the sacred Scriptures. Muslims pray oftener than the best Christians and are making converts to their faith in some parts of the world much faster than the followers of Jesus Christ. And who gave the world its most convincing demonstration of zeal in the last . . . century? Without doubt the Fascists, the Nazis and the Communists!