What is holiness? There are many man-made ideas about holiness, but those are not the pursuit of a student of the truth of the Bible. Its simplest definition looking at the original Hebrew is separation. However, there are two perspectives and two aspects of holiness. The two perspectives are God's and man's. When it comes to God Himself, there is a difference than when it comes to man. When it comes to God, holiness is His nature. He does not have to become holy. He IS holy. For example, for us holiness means separation from sin unto God (Acts 26:18). God was Holy when there was no other being or thing in existence. There was nothing for Him to be separated from, but He was holy then just as He is now. The Bible calls God the Holy One over 160 times. It says His name is holy 16 times. It says His spirit is holy 66 times. The scriptures are holy (Rom 1:2, Rom 7:12, 2Tim 3:15, 2Pet 1:21, 2Pet 2:21). Holiness is a primary governing attribute of God. The Bible not only says God loves us (Jn 3:16), it says He IS love (1Jn 4:8 & 16). God in Christ offering Himself for our sins is the greatest act of love ever accomplished. "Greater love hath no man than this, that a man lay down his life for his friends (Jn 15:13)." Yet God not only loved His friends, He loved His enemies. "For if, when we were enemies, we were reconciled to God by the death of his Son, much more, being reconciled, we shall be saved by his life (Rom 5:10). "And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled (Col 1:21)." Yet even God's love is subject to His holiness. God cannot love evil. In fact, He hates it (Deut 12:31, Ps 11:5, Prov 6:16-19). The Lord is sinless (2Cor 5:21, Heb 4:15, Heb 9:28, 1Pet 2:22). So when we are talking about the holiness of God, we are talking about His very nature. He cannot be anything but holy.
When we are talking about holiness as it pertains to man, there are a different set of parameters we must take into account. "For all have sinned, and come short of the glory of God (Rom 3:23)." We all have a tendency to sin built into our nature which we inherited from Adam (Rom 5, 1Cor 15:21-22). Adam was made in the likeness of God (Gen 1:27). When he and Eve gave birth to Seth, the replacement seed for Abel, he was made in Adam's likeness who had sinned (Gen 5:1-3). So it has gone through the generations. Sin has so tainted us that even when we try to do right we find perversion in it (Rom 7). So how can man be holy like God, like He commanded us to be (Lev 11:44-45, Lev 19:2, Lev 20:7, 1Pet 1:15-16)? There is only one way. It starts when we repent, get baptized in the name of Jesus Christ for the remission of sins, and receive the gift of the Holy Ghost (Acts 2:38). In repentance, we die to sin, in baptism we are buried with Christ, and in receiving the Holy Ghost be become partakers of His life (Rom 6:1-4, Col 2:8-12). Thus we apply the death, burial, and resurrection of Jesus to us. That is the gospel of salvation from sin to God (1Cor 15:1-4). We become partakers of the holy, divine nature of God when He puts His Holy Spirit in us (2Pet 1). Our sinful nature is not yet eliminated. So we have to kill it every day through the choices we make to deny it and follow His commandments (Rom 8:13, Col 3:5). It is a constant war even Paul found himself struggling with (Rom 6-8). We have to choose to walk in the Spirit, and not fulfill the lust of the flesh (Gal 5:16 & 25).
So holiness for a Christian is a process. There is the initial sanctification we get from our past sins when we are saved. Then there is the keeping from sin the grace of God gives us as well as the character development we go through to become more like Him. This is a school we do not graduate from until we die or the Lord comes back for us. Then comes the final sanctification when we are delivered from this body of death to live with Him forever (Rom 7:24-25, 1Cor 15:42-58). So salvation from sin to God is past, present, and future (2Cor 1:10).
What is the difference between holiness and righteousness? Holiness is the nature of God we partake of through His Spirit which sanctifies us. Righteousness is the outward acts of doing the right thing in the eyes of God by keeping His commandments (Jn 14:15, 1Jn 3:17). The word of God is like a seed which can be planted in our hearts (Mt 13:18-23, 1Pet 1:23). The Bible says that the reproductive power of the creation was placed in its seeds (Gen 1:11-12). Each kind reproduces itself according to the genetic programming God placed in its seed. When God places His word in our hearts, it will produce after its kind if we meet the conditions (Mt 3:8-10, Mt 7:16-20, Gal 5:19-23). What is in our hearts will come out in our words and deeds (Mt 12:34). That is why we must cleanse our hearts first and become partakers of His divine nature on the inside in order to produce the righteousness of God (Mt 23:26).
Some people today say holiness is outdated and old-fashioned, but God has not changed (Mal 3:6, Heb 13:8). There are many benefits to holiness. The first and most important is relationship with God. Sin separates from God (Is 59:1-2). Holiness connects with God (Heb 22 & 38-39, Jam 4:6-10). Holiness makes our prayers powerful, but sin makes them weak (Prov 15:8 & 29, Prov 28:9). Holiness frees us from the control of sin (Jn 8:31-38, Rom 6:7 & 16-23). Holiness gives us character (Gal 5:22-23). Holiness gives us access to promises for this life and the next (1Thes 4:8). Some people wonder if it is necessary or worth it to strive to be holy. It does take much effort (Heb 4:12). No effort made to pursue God is ever a waste. Even if it is unnecessary for salvation, God sees our hearts. If we are sincerely seeking to apply the word of God to the way we live, He sees that and it means something to Him. People can mock and ridicule all they want. That's what they did to Noah until the flood came, and they will do it before the Lord returns as well (2Pet 3:1-15). We can also look at it like insurance. We don't wait until an accident or disaster to apply for insurance. It's too late then. We must have the insurance before the event. It's better to have it and not need it than to need it and not have it. We are talking about eternity. The stakes are much too high to be risking our souls. Better to play it safe and be found to have been doing more than less than necessary. Also, we should always be striving for the ideal of being like Jesus, although also knowing the reality is that we come up short.
That being said, we should also know what holiness is not. It is not a set of rules. It is not a question of what we have to do. It is a privilege and opportunity of what we get to do. Holiness is the pursuit of Biblical principles, not seeking some artificial, man-made list of do's and don'ts. That what the hypocrites in the days of Jesus were doing (Mt 23, Mk 7). For example, there is no scripture that says, "Don't smoke cigarettes", but the scripture says not to harm your body because it is the temple of the Holy Ghost (1Cor 3:16-17, 1Cor 6:15-20, 2Cor 6:14-7:1). We should not be looking for ways to justify sin, but ways to be more like the Lord. Holiness is not just outward, nor is it just inward. It is both (Mt 23:5 & 23-28, Mk 7:1-23, 2Cor 7:1). Holiness is not just doing what the pastor says, although that is one component (2Thes 2:15, Heb 3:7 & 17). There are principles of holiness which apply to the outward. These are to provide an example that all can see (Mt 5:16, Rom 14:16, 2Cor 13:7, 1Tim 4:12, Titus 2:8). They are to demonstrate the separation God’s people are to have from sin and the world (2Cor 6:14-7:1, Jam 1:27, Jam 4:1-4, 1Jn 2:15-16). The very definition of holiness is separation. They are to guard against temptation (Rom 13:14, 1Cor 10:9-14). However, holiness cannot be obtained solely by the keeping of outward commandments. Holiness can only happen on the inside (Mt 23:26). Then it will manifest itself on the outside (Mt 7:17-19, Mt 13:8, Jn 15:1-8, Gal 5:22-23, Eph 5:9). Holiness is not going about to establish our own righteousness, but to be a reflection of His (Rom 10:3, Phil 3:9). Holiness is not being better than others (Is 65:5, Lk 18:11, 2Cor 10:12). In fact, humility is a key ingredient (Mt 23:12, Lk 14:11, Lk 18:14, Jam 4:6 & 10, 1Pet 5:5-6). Holiness starts and continues with realizing how far short we are while reaching for more. Holiness is not isolation. Jesus was separate (Heb 7:26), but not isolated (Mt 11:19, Lk 7:39). He never condoned sin, but He did not isolate Himself. Holiness cannot be forced. It must be chosen.