I would define "zeal" as "enthusiastic commitment, demonstrating follow-through." Zeal can be a good thing, and certainly no better than when employed in the service of God. Such zeal is always discernible because, as Paul states above, it is focused on the righteousness of God. Godly zeal is inseparable from godly character, which will always exemplify the fruits of the Spirit, including mercy and sound-mindedness.
Zeal untempered by the righteous character of God will ultimately turn a person into a human wrecking ball: arrogant, close-minded, controlling, overly sensitive, "high and mighty," and merciless - all self-righteous sound and fury. In the church, it is exemplified by those who are always finding something to condemn, always ready to run someone off, always dogmatic and insisting that their standard is THE standard, always putting people into groups and assigning them labels, always laboring to establish their own righteousness - and blind as bats to their own arrogance and cruelty.
Be zealous, yes, but always in conjunction with the work of the Spirit, always in such a way as you are drawing people to Christ rather than chasing them from Him, always conscious that, thanks to fallen human nature, we can easily go to harmful extremes even with the best of intentions driving us, always mindful that we are fellow servants of one another under one Lord: redeemed from the same fate, cleansed with the same blood, sealed by the same Spirit, destined to stand before the same judgment seat, accountable to the same commandments.
There is a very fine line between contending for truth and mounting a witch hunt. That line is knowing the righteousness of God as opposed to establishing our own. May we be ever mindful of the distinction.
"This you know, my beloved brethren. But everyone must be quick to hear, slow to speak and slow to anger; for the anger of man does not achieve the righteousness of God." - James 1:19-20
* Scripture references are from the New American Standard Bible
* Image credit: www.wallpaperswide.com
