The word of God speaks of "salvation" in three tenses - past (Eph. 2:8), present (Phil. 2:12) and future (Rom. 13:11) - or in other words, of justification, sanctification and glorification.
Salvation has a foundation and a superstructure. The foundation is forgiveness of sins and justification. Justification is more than the forgiveness of our sins. It also means that we have been declared righteous in God's eyes, on the basis of Christ's death, resurrection and ascension. This is not on the basis of our works (Eph. 2:8,9), for even our righteous deeds are like filthy rags in God's sight (Isa. 64:6). We are clothed with the righteousness of Christ (Gal. 3:27). Repentance and faith are the conditions for being forgiven and justified (Acts 20:21). True repentance must produce in us the fruit of restitution - returning money and things and taxes due, that are wrongfully in our possession (that belong to others), and apologising to those we have wronged, as far as possible (Lk. 19:8,9). When God forgives us, He also requires that we forgive others in the same way. If we fail to do this, God withdraws His forgiveness (Matt. 18:23-35). Repentance and faith must be followed by baptism by immersion in water, whereby we publicly testify to God, to men and to demons that our old man is indeed buried (Rom. 6:4,6). We can then receive the baptism in the Holy Spirit, whereby we are endued with power to be witnesses for Christ by our life and our lips (Acts 1:8). The baptism in the Holy Spirit is a promise to be received by faith, by all of God's children (Matt. 3:11; Lk. 11:13). It is the privilege of every disciple to have the witness of the Spirit that he is indeed a child of God (Rom. 8:16) and also to know for certain that he has indeed received the Holy Spirit (Acts 19:2).
Sanctification is the superstructure of the building. Sanctification (meaning `being set apart' from sin and the world) is a process that begins with the new birth (1 Cor. 1:2) and that should continue throughout our earthly life (1 Thess. 5:23,24). This is a work that God initiates in us through the Holy Spirit, writing His laws upon our hearts and minds; but we have to do our part, working out our salvation with fear and trembling (Phil. 2:12,13). It is we who are to put to death the deeds of the body through the power that the Spirit offers us (Rom. 8:13). It is we who have to cleanse ourselves from all filthiness of the flesh and the spirit, perfecting holiness in the fear of God (2 Cor. 7:1). Where a disciple is radical and wholehearted in cooperating with the Holy Spirit in this work, the work of sanctification will progress rapidly in his life. The work will obviously be slow or stagnant in the life of one whose response to the Spirit's leadings is sluggish. It is in times of temptation that our wholeheartedness in desiring sanctification is truly tested. To be sanctified is to have the righteousness of the law fulfilled inside our hearts - and not just externally as under the old covenant (Rom. 8:4). This was what Jesus emphasised in Matt. 5:17-48. The law's requirements were summed up by Jesus as loving God wholeheartedly and loving our neighbour as ourselves (Matt. 22:36-40). It is this law of love that God now seeks to write in our hearts, for that is His own nature ( Heb. 8:10; 2 Pet. 1:4). The outward manifestation of this will be a life of victory over all conscious sin and of obedience to all of Jesus' commandments (Jn. 14:15). It is impossible to enter into this life without first fulfilling the conditions of discipleship that Jesus laid down (Lk. 14:26-33). These are basically to give the Lord the first place above all our relatives and our Self-life and to be detached from all of one's material wealth and possessions. This is the narrow gate that we have to go through first. Then comes the narrow way of sanctification. Those who do not pursue after sanctification will never see the Lord (Heb. 12:14).
While it is possible to be perfect in our conscience here and now (Heb. 7:19;9:9,14), it is not possible to be sinlessly perfect until we have a glorified body at Jesus' return (1 Jn. 3:2). We can be LIKE Him only then. But we must seek to WALK as He walked even now (1 Jn. 2:6). As long as we have this corruptible body, unconscious sin will be found in it, however much we may be sanctified (1 Jn.1:8). But we can be perfect in our conscience (Acts 24:16) and be free from conscious sin (1 Jn.2:1a), even now, if we are wholehearted (1 Cor. 4:4).Thus we wait for the second coming of Christ and for our glorification - the final part of our salvation, when we will become sinlessly perfect (Rom. 8:23; Phil. 3:21).