In my experience, I often meet three different kinds of people among believers and unbelievers as relates to zeal and knowledge.
People Who Have Zeal But Without Knowledge: Zeal is not good without knowledge (Prov.19:2). Zeal without knowledge is even dangerous because it always tears down rather than builds up, and it frequently causes man to do the work of the enemy rather than of God. In Romans 10:2, Paul speaks of his countrymen as possessing a zeal that was not according to knowledge. At one time he himself was in this condition. As a result he and his countrymen rejected the gospel and persecuted the church (Phil. 3:6; Acts 22:3, 4).
Many non-Christian religious people fall into this category. For example, the Buddhists in Myanmar are very zealous for the false doctrine which they were taught. Many are sincere in their belief, but their sincerity lacks the knowledge of God. Even many Christians are often misguided by zeal without knowledge. For example, there are some Christians who are zealously promoting a false doctrine known as the “prosperity gospel.” Health and wealth are not guaranteed for any Christian. How devastating this false doctrine must be to Christians who have been particularly called by God to a life of suffering! (See Luke 9:23-25, Philippians 4:12 and 2 Timothy 3:12 for starters!)
People Who Have Knowledge But Without Zeal: Knowledge without zeal is equally dangerous. This describes many in the church today. They have heard and received God’s Word, but like the church at Sardis, they “are dead” (Rev. 3:1-3). They have become scholastic bookworms who seek to know more and more about God without knowing Him, who seek to win arguments without winning souls, who are puffed up with knowledge but lacking in love, who know the Word but fail to do what it says.
If we love to gain knowledge about God, but lack a proper zeal to serve God, then we must examine ourselves to see if we are in the faith. We must remember the warning of James—faith without works is dead (James 2:17). May the Lord rescue us from zeal without knowledge and from knowledge without zeal. The end result of discipleship is obedience. And the end result of theology must be worship.
People Who Have both Zeal and Knowledge: This is the ideal state God expects of all Christians. These individuals are busy preaching and teaching the Word in and out of season (2 Tim 4:2-5). They are zealous to help the needy, especially the needy saints (Gal 6:10). They are more than willing to declare God’s Word to anyone who asks them for a reason of the hope that is within them, with meekness and in fear (1 Thess. 5:21; 1 Pet 3:15). They are more than able to defend the gospel and contend for the faith (Phil. 1:16-18; Jude 3).
Let’s be zealously committed to Christ and His kingdom (Romans 12:11), but in our zeal may we always strive to have a zeal governed by a pure knowledge of God’s Word.