I saw this article on www.gotquestions.org. Good article and worth reading:
Question: "Can a Christian lose salvation?"
Answer: Before this question is answered, the term “Christian” must be defined. A “Christian” is not a person who has said a prayer, or walked down an aisle, or been raised in a Christian family. While each of these things can be a part of the Christian experience, they are not what “makes” a Christian. A Christian is a person who has, by faith, received and fully trusted in Jesus Christ as the only Savior (John 3:16; Acts 16:31; Ephesians 2:8-9).
So, with this definition in mind, can a Christian lose salvation? Perhaps the best way to answer this crucially important question is to examine what the Bible says occurs at salvation, and to study what losing salvation would therefore entail. Here are a few examples:
A Christian is a new creation. “Therefore, if anyone is in Christ, he is a new creation; the old has gone, the new has come!” (2 Corinthians 5:17). This verse speaks of a person becoming an entirely new creature as a result of being “in Christ.” For a Christian to lose salvation, the new creation would have to be canceled and reversed.
A Christian is redeemed. “For you know that it was not with perishable things such as silver or gold that you were redeemed from the empty way of life handed down to you from your forefathers, but with the precious blood of Christ, a lamb without blemish or defect” (1 Peter 1:18-19). The word “redeemed” refers to a purchase being made, a price being paid. For a Christian to lose salvation, God Himself would have to revoke His purchase that He paid for with the precious blood of Christ.
A Christian is justified. “Therefore, since we have been justified through faith, we have peace with God through our Lord Jesus Christ” (Romans 5:1). To “justify” means to “declare righteous.” All those who receive Jesus as Savior are “declared righteous” by God. For a Christian to lose salvation, God would have to go back on His Word and “un-declare” what He had previously declared.
A Christian is promised eternal life. “For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life” (John 3:16). Eternal life is a promise of eternity (forever) in heaven with God. God promises, “Believe and you will have eternal life.” For a Christian to lose salvation, eternal life would have to be taken away. If a Christian is promised to live forever, how then can God break this promise by taking away eternal life?
A Christian is guaranteed glorification. “And those he predestined, he also called; those he called, he also justified; those he justified, he also glorified” (Romans 8:30). As we learned in Romans 5:1, justification is declared at the moment of faith. According to Romans 8:30, glorification is guaranteed for all those whom God justifies. Glorification refers to a Christian receiving a perfect resurrection body in heaven. If a Christian can lose salvation, then Romans 8:30 is in error, because God could not guarantee glorification for all those whom He predestines, calls, and justifies.
Many more illustrations of what occurs at salvation could be shared. Even these few make it abundantly clear that a Christian cannot lose salvation. Most, if not all, of what the Bible says happens to us when we receive Jesus Christ as Savior would be invalidated if salvation could be lost. Salvation cannot be reversed. A Christian cannot be un-newly created. Redemption cannot be undone. Eternal life cannot be lost and still be considered eternal. If a Christian can lose salvation, God would have to go back on His Word and change His mind—two things that Scripture tells us God never does.
The most frequent objections to the belief that a Christian cannot lose salvation are 1) What about those who are Christians and continually live an immoral lifestyle? 2) What about those who are Christians but later reject the faith and deny Christ? The problem with these two objections is the phrase “who are Christians.” The Bible declares that a true Christian will not live a continually immoral lifestyle (1 John 3:6). The Bible declares that anyone who departs the faith is demonstrating that he never truly was a Christian (1 John 2:19). Therefore, neither objection is valid. Christians do not continually live immoral lifestyles, nor do they reject the faith and deny Christ. Such actions are proof that they were never redeemed.
No, a Christian cannot lose salvation. Nothing can separate a Christian from God’s love (Romans 8:38-39). Nothing can remove a Christian from God’s hand (John 10:28-29). God is both willing and able to guarantee and maintain the salvation He has given us. Jude 24-25, “To Him who is able to keep you from falling and to present you before his glorious presence without fault and with great joy—to the only God our Savior be glory, majesty, power and authority, through Jesus Christ our Lord, before all ages, now and forevermore! Amen.”