I know this is a topic that one would think the answer is obvious but from some encounters that I have had, the clarity of the answer to this question requires closer scrutiny.
Jesus indicated that under the Law the Jews were commanded not to commit adultery. In Matt 5:27-28 Jesus says “You have heard that it was said, ‘YOU SHALL NOT COMMIT ADULTERY’; but I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart.” There is a difference between the letter of the law and the spirit of the law. Jesus always takes us to the higher level, the spirit of the law, the righteousness of God. 2 Cor 3:5-6 “Not that we are adequate in ourselves to consider anything as coming from ourselves, but our adequacy is from God, who also made us adequate as servants of a new covenant, not of the letter but of the Spirit; for the letter kills, but the Spirit gives life.”
With the righteousness of God being the standard, even born again Christians can and do fall short. Matt 5:44-48 “But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you; That ye may be the children of your Father which is in heaven: for he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust. For if ye love them which love you, what reward have ye? do not even the publicans the same? And if ye salute your brethren only, what do ye more than others? do not even the publicans so? Be ye therefore perfect, even as your Father which is in heaven is perfect.“
The bad news is that true and perfect righteousness is not possible for man to attain on his own; the standard is simply too high. The good news is that true righteousness is possible for mankind, but only through the cleansing of sin by Jesus Christ and the indwelling of the Holy Spirit. We have no ability to achieve righteousness in and of ourselves. But Christians possess the righteousness of Christ, because “God made him who had no sin to be sin for us, so that in him we might become the righteousness of God” (2 Corinthians 5:21). This is an amazing truth. On the cross, Jesus exchanged our sin for His perfect righteousness so that we can one day stand before God and He will see not our sin, but the holy righteousness of the Lord Jesus.
I have been with professing Christians that say that they do not sin. Period – full stop. From my perspective, in my studies of the Scriptures and life experience, I think that it goes without saying that Christians do still sin. I will qualify this shortly.
“Sin” is any thought, word, or action that is contrary to the character or law of God. We all sin (Romans 3:23), and even what we consider good deeds are often tainted by selfish motives or pride (Isaiah 64:6). Left to ourselves, it is impossible to please God or to be completely free from sin (Romans 3:10; Ecclesiastes 7:10).
When we come to Christ by faith and trust Him to forgive and cleanse us of all our sin, we are in that moment born again (John 3:3). That new birth of the spirit results in a new creation (2 Corinthians 5:17). God gives the repentant sinner a new heart that is now turned toward obeying and pleasing Him rather than self (2 Corinthians 5:9; Romans 8:5–6). Whereas we were formerly slaves to sin, we are now “slaves to righteousness” (Romans 6:16). Sin’s control has been broken by the power of Jesus (Romans 6:6; Titus 2:14).
However, we still live in the flesh, and the flesh is prone to want what it wants. In Romans 7:21–23, Paul admits the battle between flesh and spirit in his own life: “So I find this law at work: Although I want to do good, evil is right there with me. For in my inner being I delight in God’s law; but I see another law at work in me, waging war against the law of my mind and making me a prisoner of the law of sin at work within me.” Each battle with temptation is won or lost based upon how fully we are surrendered to the control of the Holy Spirit (Galatians 5:16–17).
The book of 1 John was written to Christians. The apostle says, “If we claim to be without sin, we deceive ourselves and the truth is not in us. If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness” (1 John 1:8–9). It is clear from this passage that even those who have been born again and redeemed by the blood of Jesus will still sin. Through thought, attitude, or action, we will “grieve” (Ephesians 4:30) and “quench” (1 Thessalonians 5:19) the Holy Spirit at times. But this passage also reassures us that God offers continual, ongoing grace whenever we agree with Him about our sin and ask for His cleansing.
However, other passages clarify the boundaries of this ocean of grace. First John 3:6 says, “No one who lives in him keeps on sinning. No one who continues to sin has either seen him or known him.” Verse 9 says that those who have been “born of God” will not continue to live sinfully. The implication is that this is not a matter of trying harder. Rather, it is the equivalent of saying, “A fish cannot remain on land for long because its nature is to seek water.” A fish could flop onto the shore and survive for a short time. But it was not made for land and cannot continue there. When we are born again, our natures change, and we cannot continue in sin. Christ not only erases our past sin; He also transforms our hearts so that we no longer desire it (Colossians 2:13–14).
Paul asked, “What shall we say, then? Shall we go on sinning so that grace may increase? By no means! We are those who have died to sin; how can we live in it any longer?” (Romans 6:1–2). Although Christians will still sin after being saved, the heart change that the Holy Spirit brings will result in a new attitude toward sin. Sin cannot continue being a lifestyle choice if we have surrendered our lives to Jesus. That’s what it means to say that Jesus is Lord (Romans 10:9; Colossians 2:6). We have a new boss. We cannot be followers of Christ and followers of sin at the same time. They are going in opposite directions (Luke 9:23; 14:33). Romans 12:2 instructs, “Be transformed by the renewing of your mind.” Renewal can take some time, but it is a process that produces a change of behaviour.
When a true child of God goes astray, our Father administers discipline to bring him back into obedience. Hebrews 12:7–8 says, “It is for discipline that you have to endure. God is treating you as sons. For what son is there whom his father does not discipline? If you are left without discipline, in which all have participated, then you are illegitimate children and not sons.” If a professing Christian can choose a lifestyle of sin without experiencing enough discipline to bring them to repentance, then according to this Scripture, it is highly unlikely that that person is a child of God.
Do Christians sin? Yes. Do they willfully continue in sin? No. Scripture indicates that, while we will always “fall short of the glory of God” (Romans 3:23), we have the hope that the power of God is at work in us to “make us more and more like him as we are changed into his glorious image” (2 Corinthians 3:18, NLT). The NIV translation of Heb 10:14 puts it this way: “For by one sacrifice he has made perfect forever those who are being made holy.”