2 Kings 10

Then Jehu gathered all the people together, and said to them, “Ahab served Baal a little, Jehu will serve him much. Now therefore, call to me all the prophets of Baal, all his servants, and all his priests. Let no one be missing, for I have a great sacrifice for Baal. Whoever is missing shall not live.” But Jehu acted deceptively, with the intent of destroying the worshipers of Baal. vv.18-19

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"At first, as we read this verse, it seems alarmingly as if Jehu has given up his great zeal for the LORD, and is about to let Him down in a major way. But we mustn’t jump the gun here, for we learn what is really going on in the next verse. Here, we see that the impression we might have gotten at first in the last verse was wrong. Jehu was not turning his back on the LORD. Instead, he is now planning to go far beyond simply wiping out the wicked family of Ahab. Now, he wishes to wipe out the idolatrous worship of Baal that Ahab and Jezebel had imported into the land of Israel. He was being zealous indeed! He was moving beyond merely keeping the command the LORD had given him, and was attempting to serve Him with all his heart and life. Now, we see how his plans worked out in the next verses...Interestingly, Jehu actually performs a burnt offering to Baal before springing his trap. I believe that he was being careful again. If any of those present had not sacrificed to Baal before, he wanted to be certain that they had now, so that they would at least be guilty of that before he had them slain. Thus, he ensured with all finality that none who were innocent would be slain with the guilty. Then, once this is finished, the trap is sprung, and the worshippers of Baal wiped out by the soldiers of Jehu...this was not something that God had commanded him to do. This was done on Jehu’s own initiative. The LORD had only commanded Jehu to wipe out the family of Ahab. Yet in his zeal, Jehu did this, and the LORD blessed him in it. This seems like a very harsh thing to do to us, to slaughter all these people like this, worshippers of false gods or not. Yet what Jehu did was just as he should have done according to the law of Moses in Deuteronomy 17:2-5" (Nathan Johnson, Precepts.wordpress.com).  
How can you have zeal like Jehu for the Lord?  Have you ever been in a situation like Jehu surrounded by all non-worshipers of the Lord and had pretend to follow another god?  Was it out of fear of men or out of ultimately glorifying God?