I read your answer about re-baptism. For a time now I have struggled with about being re-baptized. When I was originally baptized, it was done the proper way by immersion in the name of the Father, of the Son, and Holy Spirit for the purpose of becoming saved. But since then I fell away from Christ for a couple of years. I literally told people I wasn't a Christian anymore because I didn't want to disgrace God and who He is and have people get the wrong idea about what a Christian is. Even though from my own reading, which I have read through the New Testament many times and the Old Testament a couple times, I don't find merit for being re-baptized; but at the same time I wonder if I should, since I denied to being a Christian. I know (I forget where) the only thing people are told to do to come back to the faith or get back on track are to do the things they did in the beginning: from good works, to serving God, repentance, etc. These don't include baptism because baptism is a part of becoming saved. I think I know the answer and I have been in prayer about it, but doubt still fills my mind at times. There's that part of me, that wants to know I'm for sure secured in God by being re-baptized again, but the other part of me is like you know the Scripture somewhat and you know it has no basis, then why do it? I know this is probably an easy question but insight would be great.
You are not the first to ask whether unfaithfulness requires re-baptism. When I'm asked, I ask several questions about the original baptism.
1) Did you know what you were doing when you were first baptized?
2) Did you do it because of personal conviction, or were you simply following others?
3) Can you say with confidence that if you had died shortly after your original baptism that you would have gone to heaven?
The answers will greatly vary between individuals and I won't begin to guess at your answer. However, let's examine some basic, fundamental facts.
First, becoming a Christian is not a guarantee that you will remain faithful. Even the apostle Paul acknowledge that it was possible for him to fall from grace. "But I discipline my body and bring it into subjection, lest, when I have preached to others, I myself should become disqualified” (I Corinthians 9:27). Paul also talked of others who had lost their faith. Paul told Timothy that “having faith and a good conscience, which some having rejected, concerning the faith have suffered shipwreck, of whom are Hymenaeus and Alexander, whom I delivered to Satan that they may learn not to blaspheme” (I Timothy 1:19-20). Hymenaeus and Alexander were sailing the seas of faith, but they suffered a shipwreck – they had lost their faith. See Once Saved, Always Saved? for more details.
Second, an unfaithful Christian is still a Christian. When a Christian strays from the faith, other Christians are to withdraw contact with him to express disapproval with his choice. "And if anyone does not obey our word in this epistle, note that person and do not keep company with him, that he may be ashamed. Yet do not count him as an enemy, but admonish him as a brother" (II Thessalonians 3:14-15). Even lost, a fallen Christian is still counted as a brother -- a fallen brother, but a brother none the less.
Third, there is a way for unfaithful Christians to turn their lives around. The primary teaching on this matter is found in I John. "If we say that we have fellowship with Him, and walk in darkness, we lie and do not practice the truth. But if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin. If we say that we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. If we say that we have not sinned, we make Him a liar, and His word is not in us. My little children, these things I write to you, so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous" (I John 1:6 - 2:1). What God asks of a fallen Christian is to admit to God that he has sinned and to ask for forgiveness. God then promises to forgive us of our sins. For some, this is a difficult step because there is nothing to show for the request. In becoming a child of God, the final act is baptism thus there is at least being wet to show that we took some action. Yet in asking God to forgive our sins, we must fully trust that God will keep His promise.
There is also a need to make changes in your life. Here we can see actual results. We cannot claim to have truly returned from sin if nothing in our life has changed. "Now I rejoice, not that you were made sorry, but that your sorrow led to repentance. For you were made sorry in a godly manner, that you might suffer loss from us in nothing. For godly sorrow produces repentance leading to salvation, not to be regretted; but the sorrow of the world produces death. For observe this very thing, that you sorrowed in a godly manner: What diligence it produced in you, what clearing of yourselves, what indignation, what fear, what vehement desire, what zeal, what vindication! In all things you proved yourselves to be clear in this matter" (II Corinthians 7:9-11). See Repentance for further details.
Still there is the matter of your doubts. They should not be ignored but seriously addressed. An expression of doubt can mean that your faith remains weak -- that you haven't fully given your trust to God. We need to develop within ourselves the level of trust that Paul expressed: "For this reason I also suffer these things; nevertheless I am not ashamed, for I know whom I have believed and am persuaded that He is able to keep what I have committed to Him until that Day" (II Timothy 1:12).
Doubt is detrimental to faith. "Do you have faith? Have it to yourself before God. Happy is he who does not condemn himself in what he approves. But he who doubts is condemned if he eats, because he does not eat from faith; for whatever is not from faith is sin" (Romans 14:22-23). Going back to those questions I asked at the beginning, if there is the lest doubt in your heart that you were not truly converted when you were originally baptized, I would recommend fixing those deficiencies and be baptized again. At best it will correct a problem and assure your faith in God. It will also declare to world that you have rededicated your life to God. At worse, you took a dunking for no particular purpose in God's eyes.
Being baptized is compared to the Old Testament practice of being circumcised. "In Him you were also circumcised with the circumcision made without hands, by putting off the body of the sins of the flesh, by the circumcision of Christ, buried with Him in baptism, in which you also were raised with Him through faith in the working of God, who raised Him from the dead" (Colossians 2:11-12). The very nature of circumcision is an act that can be performed only once. Similarly, baptism is related to marriage. "Husbands, love your wives, just as Christ also loved the church and gave Himself for her, that He might sanctify and cleanse her with the washing of water by the word, that He might present her to Himself a glorious church, not having spot or wrinkle or any such thing, but that she should be holy and without blemish" (Ephesians 5:25-27). Marriage is for life. Some renew their vows, but that renewal doesn't make the original vow of non-effect or say that the couple was any less married prior to the renewal. Renewed vows have no true effect on a marriage, but still some people like to have the reminder.