The twentieth-century evangelist Billy Sunday once said, "If there is no joy in religion, you have got a leak in your religion." Does your Christianity have a leak somewhere?

Paul the apostle was so anchored in Jesus Christ that even from a jail cell he couldn't help but be joyful--and he wanted to safeguard the Philippians' joy, too. He wrote to them, "Finally, my brethren, rejoice in the Lord. For me to write the same things to you is not tedious, but for you it is safe. Beware of dogs, beware of evil workers, beware of the mutilation! For we are the circumcision, who worship God in the Spirit, rejoice in Christ Jesus, and have no confidence in the flesh" (Philippians 3:1-3).

In these verses, Paul gave the Philippians three defenses to keep their joy from leaking:

1. Joy must be guarded. The command "Rejoice in the Lord" is in the present active indicative, meaning "Go on constantly rejoicing in the Lord." That tells me joy is a choice you make. Notice also the command is to rejoice "in the Lord." Joy is a by-product of your relationship with the living Lord of the universe. And it must be guarded, for Paul knew there were joy-stealers and grace-killers out there.

2. Legalism must be avoided: "Beware of dogs, beware of evil workers, beware of the mutilation!" (v. 2). Paul was warning the Philippians against false teachers called Judaizers, who said that Gentiles had to submit to Jewish rules in order to be right with God (see Acts 15:1). Anyone who thinks they can get right with God by following certain rules or doing good works is in effect saying, "The work of Jesus Christ on the cross was not good enough." That's a vicious, destructive teaching. It mutilates the grace of God and the work of Christ--thus it needs to be avoided.

3. Identity must be comprehended. In verse 3, Paul described what a true Christian believer looks like in contrast to false religious legalists: We are the spiritually circumcised, those with a true inward cleansing, and we worship God authentically. We also rejoice--or boast--in Jesus and what He's done for us, depending totally on His work.

Let's say you decided to take a road trip to Rocky Mountain National Park. On the way, you notice people pushing their vehicles along the road. When you stop to get gas, one of these people comes up to you and says, "I used to drive, too, but I'm a lot smarter now, so I push. You really ought to, too." Let's say you're dumb enough to do just that, and you push your car all the way up those mountain passes and back home again. Are you going to be joyful doing that? No way--you'll be miserable.

The legalist message is that you have to work your way to heaven--push your car up the mountain, so to speak. But our message is the gospel: Jesus paid it all. All you have to do is give Him the keys, hop in the backseat, and let Him take over. That's where ultimate joy comes from--and it can't be taken away.