Let's begin by defining what a saint is. Throughout the Apostle Paul's epistles to various churches, he addresses all believers in Christ as saints (Romans 1:7; 1 Corinthians 1:2; 2 Corinthians 1:1; Ephesians 1:1; Philippians 1:1; Colossians 1:2; 1 Timothy 5:10; Philemon 1:5). A saint is a person who has been chosen and set apart by God, is justified by faith in Jesus Christ, is sanctified by the Spirit of God, offers their lives in sacrificial service to God, and pursues holiness in both motive and practice (1 Peter 2:9–10; Romans 10:10; 12:1; 1 Corinthians 1:2; Hebrews 9:14; 12:14).
Each and every true believer in Christ is a saint. There are no classes in Christianity where some are saints and some are common. Galatians 3:27–29 says, "For as many of you as were baptized into Christ have put on Christ. There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus. And if you are Christ's, then you are Abraham's offspring, heirs according to promise." First Peter 2:9–10 says, "But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light. Once you were not a people, but now you are God's people; once you had not received mercy, but now you have received mercy."
There are a few different ways in which the Christian's sainthood can be viewed. All Christians ARE saints, and ARE CALLED TO BE saints.
We see this in Paul's letters to the Corinthians. First Corinthians is addressed, "To the church of God that is in Corinth, to those sanctified in Christ Jesus, called to be saints together with all those who in every place call upon the name of our Lord Jesus Christ, both their Lord and ours." Similarly, 2 Corinthians 1:1 is from, "Paul, an apostle of Christ Jesus by the will of God, and Timothy our brother, To the church of God that is at Corinth, with all the saints who are in the whole of Achaia."
What does this mean? All Christians are righteous and holy in God's sight through faith in Jesus Christ. The Christian's sins have been washed away and the righteousness of Christ has been credited to him/her. A Christian's legal or positional standing before God is that he/she is declared righteous. In this sense, Christians ARE saints.
However, although God has broken the power and penalty of sin over the life of a believer, He has not eradicated its presence. The sin nature, which is called "the flesh," remains in a believer until they leave this body and go to be with the Lord. While in this body, the Spirit of God, who dwells in the believer, wages continuous war against the remaining sin nature. Christians are commanded to cooperate with the Spirit of God in this spiritual warfare. They must discipline themselves, deny themselves, walk in the Spirit, be filled with the Spirit, and not grieve the Spirit (Galatians 5; Colossians 3; Ephesians 4). If they do so, they will grow in spiritual maturity and conformity to Christ (2 Corinthians 3:17–18). In this sense, Christians are called to be saints. They are called to pursue that holiness which Christ has obtained for them.
However, even after being justified and during the sanctification process that takes place throughout the rest of a believer's life on Earth, Christians will continue to sin, albeit increasingly less so and experiencing conviction and repentance when they do so. It is a true believer's greatest burden, struggle, and sorrow that they sin.
Paul wrote in Romans 7:15–25 "For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. Now if I do what I do not want, I agree with the law, that it is good. So now it is no longer I who do it, but sin that dwells within me. For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. For I do not do the good I want, but the evil I do not want is what I keep on doing. Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me. So I find it to be a law that when I want to do right, evil lies close at hand. For I delight in the law of God, in my inner being, but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members. Wretched man that I am! Who will deliver me from this body of death? Thanks be to God through Jesus Christ our Lord! So then, I myself serve the law of God with my mind, but with my flesh I serve the law of sin." John wrote, "If we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness" (1 John 1:8-9).
It is not until the Christian is delivered completely from this "body of death" that he or she will be entirely free from the practice of sin. The departed saints who are currently in the presence of the Lord do not continue to sin. Therefore, excepting the departed saints, Christians are sinners who have been saved and made saints; yet they are saints who sin, but whose sin is forgiven. Of course, after a Christian has been glorified, he or she will forever be a saint who never sins. Christians will be always with and like the Lord Jesus Christ. Perfect.
Romans 8:30 assures us, "And those whom he predestined he also called, and those whom he called he also justified, and those whom he justified he also glorified." Philippians 3:20–21 says, "But our citizenship is in heaven, and from it we await a Savior, the Lord Jesus Christ, who will transform our lowly body to be like his glorious body, by the power that enables him even to subject all things to himself." First John 3:2 declares, "Beloved, we are God's children now, and what we will be has not yet appeared; but we know that when he appears we shall be like him, because we shall see him as he is."