What are Christians to think about their sanctification? Is it immediate and instantaneous, or is it only progressive and slowly develops over time? The Bible gives us some clear teaching in answer to these questions. By definition, when a person becomes a Christian he is made to be “holy” and “righteous” in God’s sight (1 Cor. 1:2; 1 Cor. 6:11; 1 Pet. 2:9-10). This fundamental change is made possible by the imputation of Christ’s righteousness to the individual Christian (2 Cor. 5:21). Since that person is united with the risen and reigning Christ, he is justified, adopted, and sanctified. These glorious doctrines witness to the change of one’s position in and through Jesus Christ. Yet, the Bible also teaches that individual Christians are to make serious efforts, by God’s grace, to improve his condition through holy living (Rom. 12:1; Eph. 4:17-24; Col. 3:12-17). Hence, through these efforts the Christian progressively grows in his sanctification. It is a cooperative effort—God works, and the Christian works (Phil. 2:12-13). This is why the Bible defines Christians as “saints and faithful brothers” (Col. 1:2), and also gives strong exhortations such as “You shall be holy, for I am holy” (Lev. 11:44; 1 Pet. 1:16).