A man may be long-suffering in promoting the interests of his own beliefs or church, and be ready to die for the peculiar opinions of his own religious denomination, and yet have no real love for Christ. Such was the zeal of the Pharisees. This is a false zeal. J. C. Ryle explains:
“It is always good to be zealous in a good cause.” (Galatians 4:18)
Alas, I fear there are many professing Christians who if they had lived in the days when our Lord and His apostles walked upon earth, would have called Him and all His followers enthusiasts and fanatics. There are many, I fear, who have more in common with Annas and Caiaphas—with Pilate and Herod—with Festus and Agrippa—with Felix and Gallio—than with Paul and the Lord Jesus Christ. . . .
There never was a grace of which Satan has not made a counterfeit. There never was a good coin issued from the mint—but forgers at once have coined something very like it. It is one of Satan’s devices to place distorted copies of the believer’s graces before the eyes of men, and so to bring the true graces into contempt. No grace has suffered so much in this way as zeal. Of none perhaps are there so many shams and counterfeits abroad. We must therefore clear the ground of all rubbish on this question. We must find out when zeal in religion is really good, and true, and of God.
Reader, if zeal be true, it will be a zeal according to knowledge. It must not be a blind, ignorant zeal. It must be a calm, reasonable, intelligent principle, which can show the warrant of Scripture for every step it takes. The unconverted Jews had zeal. Paul says, “I bear them record that they have a zeal of God—but not according to knowledge.” (Rom. 10:21) Saul had zeal when he was a persecuting Pharisee. He says himself, in one of his addresses to the Jews, “I was zealous toward God, as you all are this day.” (Acts 22:3) … They were all zealous. They were all in earnest. But their zeal was not such zeal as God approves—it was not a “zeal according to knowledge.”
Furthermore, if zeal be true, it will be a zeal from true motives. Such is the subtlety of the heart, that men will often do right things from wrong motives. Amaziah and Joash, kings of Judah, are striking proofs of this. Just so, a man may have zeal about things that are good and right—but from ulterior motives, and not from a desire to please God. And such zeal is worth nothing. It is reprobate silver. It is utterly lacking when placed in the balance of God. Man looks only at the actions. God looks at the motives. Man only thinks of the quantity of work done. God considers the doer’s heart. (“Be Zealous”)