If you read through the Bible you can’t help but pick up the idea that the God of the Bible is holy, and wants His people to be Holy. Holiness is an important theme that runs throughout the Scriptures. In fact, the words holy and holiness are used more than nine hundred times in the Bible. In the Old Testament the word that is most often translated as holy very literally means, “to cut” or “to separate.” Therefore to be holy kind of means to be cut away, or separated from what is unclean and sinful and to be totally dedicated to what is clean and pure.
In the Old Testament God’s holiness is His transcendence over creation and the perfection of his character. God is holy in that He is distinct from his creation and has power over it. His holiness is especially mentioned in the Psalms, and the Prophets. In the Old Testament God is called “Holy” (Isaiah 57:15), “The Holy One” (Job 6:10; Isaiah 43:15), and “The Holy One of Israel” (Psalm 89:18; Isaiah 60:14; Jeremiah 50:29). The holiness of God in the Old Testament also teaches us that God is separate from all that is evil and impure. His holiness sets the standard for what purity is.
Throughout the New Testament we read about the importance for practical everyday holiness in lives of believers. The same God that declares a person righteous through faith in Jesus also commands believers to be holy.
“but as He who called you is holy, you also be holy in all your conduct, because it is written, ‘Be holy, for I am holy.’” 1 Peter 1:15-16 (NKJV)
The necessity of holiness is something that is often minimized in our world today. It is not uncommon to see people professing faith in Jesus while living in lifestyles the Bible calls sinful. There are all kinds of cultural justifications given for this. However, do these cultural justifications stand up to the scrutiny of Scripture?
“Whoever commits sin also commits lawlessness, and sin is lawlessness. 5 And you know that He was manifested to take away our sins, and in Him there is no sin. 6 Whoever abides in Him does not sin. Whoever sins has neither seen Him nor known Him. 7 Little children, let no one deceive you. He who practices righteousness is righteous, just as He is righteous. 8 He who sins is of the devil, for the devil has sinned from the beginning. For this purpose the Son of God was manifested, that He might destroy the works of the devil. 9 Whoever has been born of God does not sin, for His seed remains in him; and he cannot sin, because he has been born of God.” 1 John 3:4-9 (NKJV)
As we read these verses they seem hard. I mean does being a Christian mean we never sin? On the surface that really does seem to be what these verses say. But remember, we must always compare Scripture with Scripture, and Scripture never contradicts Scripture. So let’s see if this is what this means when compared with other verses.
Earlier in this book John said that if we say we have no sin we are deceiving ourselves and the truth isn’t in us (1John 1:8). He also said that he was writing this book so that we would not sin but if we did sin, then Jesus was the atoning sacrifice for our sins and our advocate with the Father (1 John 2:1). Keep in mind that that John is writing to Christians. So first we are told that if we say we have no sin we are self-deceived and refusing to accept the truth. Secondly we are told that we shouldn’t sin, but if we do Jesus died for our sins and is our advocate. Since John says this, it is obvious that this cannot mean that a true Christian never sins. So what does it mean?
I think the best explanation is that John is referring to habitual sin. This is one of those instances where knowing Greek is quite beneficial. Since I don’t know Greek, let me defer to Dr. John MacArthur. “The best way to find out what John means is to understand the tenses in the Greek text. In verses 6 and 9 John uses the present tense, which expresses habitual, continuous action. Verse 6 literally translates, ‘Whosoever abides in him does not continually, habitually practice sin.’ Verse 9 translates, ‘Whosoever is born of God does not continually, habitually practice sin.’” Do Christians sin? Sometimes. Do they sin deliberately? Sometimes. But if they are true Christians, they will respond with grief and repentance (Ps. 51). Unsaved people live lives of habitual sin…But Christians do not live lives of habitual sin, and that is the thesis of 1 John 3:4-10.”
In other words holiness and the desire for holiness is a sign of someone that possesses eternal life. Of course, we see in this passage that the reason for our holiness is that we have been born again. Or as John puts it in verse 9, we have been born of God. Through our faith in Jesus, we have been born again and are now the children of God. This changes everything. One of the changes that is made is in regards to holiness. The children of God become holy as their heavenly Father is Holy. Followers of Jesus become holy as their Lord and Savior is holy. This is so important that the author of Hebrews will write that we are to pursue holiness because without holiness no one will see the Lord (Hebrews 12:14).
So is holiness necessary for the genuine believer? Yes it is. Holiness and the desire for holiness should characterize those who have been genuinely saved. A person who guiltlessly lives a lifestyle of sin should question the genuineness of his or her salvation.
For further study read 1 Corinthians 6:9-10, Galatians 5:19-21 and Revelation 21:8. Do those who live in the lifestyles described have any part in the Kingdom of God? Will they go to heaven? Are they genuinely saved?
Also read Hebrews 12:5-11. What does this say about a person who can guiltlessly live in sin and never experience discipline from God?
 From the sermon Why Christians and Sin are Incompatible