Philippians 3:17 Brothers, join in imitating me, and keep your eyes on those who walk according to the example you have in us. 18 For many, of whom I have often told you and now tell you even with tears, walk as enemies of the cross of Christ. 19 Their end is destruction, their god is their belly, and they glory in their shame, with minds set on earthly things.
There are many people who call themselves Christians but are actually enemies of the cross of Christ. Jesus warns us in Matthew 7:21 that not everyone who claims to be a Christian is a Christian. He said that only those who seek to do what He teaches are true believers. Paul warns the Ephesian elders of the danger of those who claim to be Christians and are not in Acts 20:26-31. He said they are like wolves among sheep. In Philippians 3:18 we read that Paul often warned the Christians to be alert for those who claim to be Christians and are not. We need to warn those in our sphere of influence to be alert for people who claim to be Christians but are actually enemies of the cross of Christ. We need to be alert to protect the Body of Christ, our family and our friends. We need to be alert to warn those who claim to be Christians to examine themselves to determine if they are in the faith.
Philippians 3:19 gives us a picture of the "enemies of the cross". Their end is destruction. Why? They haven't truly believed the gospel (Christ died on the cross, rose from the dead and is Lord). Real belief causes a person to desire to obey the teachings of Jesus by the power of the Holy Spirit and people who say words without a desire to live the life of Christ may have never really believed. The god of enemies of the cross is their belly. These people care more about satisfying their physical appetite than about serving the Lord Jesus Christ. Enemies of the cross glory in what they should be ashamed of. Enemies of the cross have their mind on earthly things. In Matthew 16:23 Jesus told Peter that he was a hindrance to Him because he had his mind on the things of men rather than on the things of God.
Paul used his life as an example of a true Christian. We need to be an example of a true Christian. Jesus gave us four characteristics of a true Christian. A true Christian will: (1) deny himself, take up his cross and follow Jesus; (2) be willing to lose his life for Jesus' sake; (3) put Jesus first above all relationships; (4) be willing to give up everything to be a disciple of Jesus (Matthew 16:24-25; Luke 14:26,33).
We are to be an example of a true follower of Jesus Christ and are to warn those in our sphere of influence about those who claim to be Christians, but really aren't. When we truly realize we have sinned and Jesus' death on the cross is the only solution for our sin, we will stop being obedient to sin which leads to death and begin being obedient to Jesus Christ which leads to righteousness (Romans 6:16).