We begin with the word sanctification, it is translated from the Greek word hagiasmos (see I Thess. 4:3-4). The root word is hagios which means separate and is included in words translated sanctify, saint, holy and hallow. All have the connotation of being separate especially separated to God from evil. These words are applied to both things as well as people and can be a verb, noun or adjective. Other words related to this one is such as cleanse, purify and consecrate. When we think in terms of biblical theology, we see how that believers have been set apart unto the Lord our God through faith in the finished work of our Lord Jesus Christ. In the Scriptures we see sanctification as both an act and as a process. There are those who propose three tenses to sanctification as three tenses to our salvation. The first and that which is the act of sanctification, being that we have been saved from the penalty and rule of sin in our lives. We know that we have been saved from the penalty of sin which is death because the life we are given in Christ is everlasting or eternal life (John 3:16, 36; 5:24), it is not hope so or maybe life if certain conditions are met. We read, “Love has been perfected among us in this: that we may have boldness in the day of judgment; because as He is, so are we in this world.” (I John 4:17). Love has been perfected in us, that is the love of God has found its completion in the work of salvation on our behalf. Now we are in Christ and as He is, so are we in this world. Our Lord took on the judgement of sin upon Himself on the cross and will never again suffer that judgment and we are in Him so that the judgment and wrath of God will never fall upon us. Therefore, we read, And this is the testimony: that God has given us eternal life, and this life in in His Son. He who has the Son has life; he who does not have the Son of God does not have life. These things I have written to you who believe in the name of the Son of God, that you may know that you have eternal life, and that you may continue to believe in the name of the Son of God.” (I John 5:11-13). We know that we have been set free from the rule of sin as well as the penalty as we see in Romans 6, with such verses as; “For sin shall not have dominion over you, for you are not under law but under grace.” (vs 14), “And having been set free from sin, you became slaves of righteousness.” (vs 18), “But now having been set free from sin, and having become slaves of God, you have your fruit to holiness and the end, everlasting life.” (vs 22). In the verb forms of I John we see that we will commit sin but we do not habitually sin, because sin no longer reigns over us. We also know that once saved or once sanctified, we are always sanctified is found in the grammar of the New Testament Believers are called saints, those who have been sanctified, irrespective of their attainments (I Cor. 1:2; Eph. 1:1; Col. 1:2; Heb. 10:10; Jude 3). In I Corinthians 6:11 believers are referred to as sanctified and in II Thessalonians, we have been chosen and sanctified. All these references are in the past tense, it is an act already completed. As to the 2nd tense and the process of sanctification, which seems to be so troublesome to so many, we find commands in Scripture that we are to be holy, to separate ourselves from sin or to be sanctified in our daily lives. Again, in Romans 6 we read, “And do not present your members as instruments of unrighteousness to sin, but present yourselves to God as being alive from the dead, and your members as instruments of righteousness to God.” (vs 13) and that well known passage, “I beseech you therefore, brethren, by the mercies of God, that you present your bodies a living sacrifice, holy, acceptable to God, which is your reasonable service.” (12:1). In Galatians 5 we are told to be led by the Spirit and produce the fruits of the Spirit (vs 18, 22,23). In the book of Ephesians, we see our position in the heavenlies in the first 3 chapters and then our practice in our daily lives in the last 3 chapters. We are seated in the heavenlies in Christ all because of the sovereign work of the Father, Son and Holy Spirit, but then we are to order our conduct in the sphere of love, light and circumspectly (chapt. 5). We are to be filled with the Spirit and submit to one another in the fear of God (Eph. 5:18,21). We are to be holy as He is holy in all of our conduct (I Peter 1:15-16). And many other Scriptures as well. So, what is this all about, why can we not just sit back and let our sanctification take over by remote control? The reason may only be known by the Lord our God, but one possibility is love is proved by obedience (I John 5:3). In our serving the Lord as Lord and obeying Him in our practical holiness, we prove our love for Him and we glorify Him as lights in a very dark world. That others may look on our lives and see that there is a God in heaven and He has spoken through His Word and in His people. It is important to keep in mind that only believers who have the Holy Spirit within them will have the desire or the ability to work toward holiness, the nonbelievers are dead in trespasses and sins and cannot do so, because a dead man cannot live a holy life, no matter how hard they try. The 3rd tense goes back to the act of sanctification and that is that one day we will be separated from the presence of sin. Such as we read: For we know that if our earthly house, this tent, is destroyed, we have a building from God, a house not made with hands, eternal in the heavens. For in this we groan, earnestly desiring to be clothed with our habitation which is from heaven, if indeed, having been clothed, we shall not be found naked, for we who are in this tent groan, being burdened, not because we want to be unclothed, but further clothed, that mortality may be swallowed up by life. Now He who has prepared us for this very thing is God, who also has given us the Spirit as a guarantee. So, we are always confident, knowing that while we are at home in the body, we are absent from the Lord. For we walk by faith, not by sight. We are confident, yes, well pleased rather to be absent from the body and to be present with the Lord. This is the hope and ultimate sanctification to which we look forward. (see also Lectures in Systematic Theology by Henry C. Thiessen)