1Eph 1:4; 1 Cor 6:11; 2 Thes 2:13; ²Rom 6:4–6; ³Eph 4:23–24; ⁴Acts 11:18; 1 Jn 3:9;
⁵Jude 20; Heb 6:11–12; Eph 3:16–19; Col 1:10–11; ⁶Rom 6:4, 6, 14; Gal 5:24

While justification and adoption are said to be acts of God’s free grace (see WLC 70, 74), sanctification is a work of God’s grace. This is because sanctification unlike justification and adoption is a continuous and gradual operation of God the Spirit in the soul of the justified sinner. It is a work that begins at our regeneration and continues throughout our lifetime.

This is what the apostle Paul is referring to when he tells us that we are chosen "to salvation through sanctification of the Spirit" (2 Thes 2:13). A Christian is said to be saved when he is justified, but there is sense in which his salvation is future, for it pleased God to leave a remnant of corruption in us, which He will only remove at our glorification at the end of this life’s journey. Nevertheless, God does not leave us in the state of corruption with which we enter His kingdom. Having given us a new birth, He continues to cause us to grow as new creatures so that we die more and more unto sin, and live more and more in actual holiness. It is God’s will that we "should be holy" (Eph 1:4) as He is holy (1 Pet 1:15-16). We are, in other words, not just given a new status (in justification and adoption), but little by little, day by day, we are being freed from the remnant of our love for sin. Our habits and inclination are being made more and more to conform unto God’s even in this life so that we are said to "walk in newness of life" (Rom 6:4).

Our Catechism teaches us several important truths about this work of sanctification.

We have already mentioned, firstly that it is a process of cultivating holiness; and secondly that it is wrought in the heart of the elect by the Holy Spirit.

But thirdly, the basis of our sanctification is the death and resurrection of Christ: "Who gave himself for us, that he might redeem us from all iniquity, and purify unto himself a peculiar people, zealous of good works" (Tit 2:14). By Christ’s death, the penalty due to our sins is removed so that we need not be punished for them by spiritual death or the effects of sin, which include further sin (cf. Rom 1:24, 26, 28). And by Christ’s resurrection, we who are united to Him are guaranteed the operation of the same resurrection power in this life in our sanctification and in the last day at our resurrection. If Christ the head experienced this power on our behalf, how could the Church, His body not have a share of it?

Fourthly, the scope of our sanctification is "the whole man." That is to say it does not only touch one or two aspects of our soul, but every aspect of it, including our intellect, and will, and we may add: emotions and inclinations.

Fifthly, the pattern or ideal according to which the Holy Spirit carries out His work of sanctifying us is the "image of God." Man was created in this image, but was defaced by the fall, though not completely obliterated. In sanctification, we are being renewed in the whole man after the image of God. And this image is characterised chiefly by true knowledge, righteousness and holiness (Eph 4:23; Col 3:10).

Sixthly, and finally, as to the relationship between sanctification and other graces in our order of salvation, we are taught that sanctification adds nothing, but causes the other graces already planted in us,—such as repentance and faith,—to be "stirred up, increased, and strengthened." W