The idea of spiritual growth, or spiritual maturity, is closely related to the doctrine of sanctification. Positional sanctification takes place instantly at the time of salvation when, having placed their trust in Jesus Christ and His finished work of redemption alone (i.e. His death, burial, and resurrection), believers are identified with Christ in God’s sight and “set apart” (i.e. sanctified) according to God’s will and purpose.
Practical sanctification, however, is a process that takes time. As new believers begin their new life “in Christ” they grow spiritually as they learn God’s Word and properly apply it to their lives. Having called on believers to “present your bodies a living sacrifice,” the Apostle Paul explains that this is accomplished through “the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God” (Rom. 12:1-2).
The believer’s mind is “renewed” as they put off the values, philosophies, and thought patterns of the world and replace them with grace thinking which includes a new values system and pattern of conduct. You see the system by which we think will set the standard by which we conduct ourselves. We are admonished to “Let this mind [way of thinking] be in you which was also in Christ Jesus” (Phil. 2:5). The point Paul is making is that Christ gave Himself wholly to do the Father’s will and so should we. True spiritual growth is marked, not by how much Scripture we know or how precisely we have honed our doctrine, but rather by how much we actually apply the Word of God, rightly divided, to our own life. Another way to put it is that the more we learn to trust God, and reflect that trust in every aspect of our life, the more spiritually mature we are. The evidence of spiritual maturity is not simply knowledge of the Scriptures, but the demonstration of that knowledge through love (see 1 Cor. 13:1-13; Eph. 3:16-19; 4:15-16; 5:1-2; Phil. 2:1-4). The knowledge of Christ’s love for us should cause us to love Him in such a way that it is demonstrated in our attitude, conduct, and commitment to serve God. Spiritual maturity is marked by spiritual knowledge being put into action.