Many times we have the flimsy repeat after me evangelism where people are certain they are saved because they said a prayer instead of trusted the Lord Jesus Christ. I remembered the number of times Paul David Washer said for the nth time about people who say that they know a person is saved in spite of their wickedness because at one moment they said a prayer. This is really false assurance because even if salvation is neither earned nor maintained by doing good works but if the salvation does not result to good works then something is terribly wrong. Many people who I preach true and false conversion to say that I am teaching them works salvation, they say they tried to be humble and they may have ignored the rest of the Bible's verses then they start their nasty game of name calling.
Some of you may say, "Some people got saved because of the sinner's prayer." The truth is they were saved in spite of it, not because of it. I have observed some preachers who lead others in the sinner's prayer but by the time the person is led in prayer, there was already genuine repentance of sin. The preacher is a hard preacher who preaches about repentance of sin and the Lord Jesus Christ. He does not go like, "Do you want to know how you can start a relationship with Jesus?" but instead, he preaches Hell and repentance to drive people to conviction. Sometimes, these pastors say, "Do you want to pray in your own words now? Go ahead." In spite of having a sinner's prayer evangelism but the whole process of proper evangelism led people to really repent and believe the Gospel of Jesus Christ. You also have these pastors who in spite of their use of the repeat after me sinner's prayer warn those who are still in sin that they are false converts.
There is a truth that Christians can fall into sin, they are not perfect, they are still in the process of being perfected and they can fall into carnality. 1 Corinthians 3:1-2 addresses the problem of newborn believers but to say that a Christian can progress in life without producing any fruit or that grace gives a license to sin is really demonic. 1 Corinthians 6:9-11 shows the difference between the saved and the unsaved. When you were not saved, you were not worthy of anything but damnation but now you are saved, you no longer life a lifestyle of sin. There ought to be a change in the life of the person because they are saved. Hebrews 12:5-7 makes it impossible for the Christian to sin all they please because God lovingly chastises them. Titus 2:11-14 shows real grace is life transforming meaning that a person cannot remain in their sinfulness for long.