If you should ask me that question, I could rightly say without being dismissive of you: “That depends.” In response, you might ask another question: “What does it depend upon?” And if I could tell that you really wanted a satisfying answer, I would be glad to explain further from the Word of God.
First of all, we must discern the meaning of the word “sanctification” within its context in any given passage of Scripture. Standing alone and apart from any context, sanctification has this meaning: to be set apart for a particular purpose. In light of that, we will now look at the three main aspects of sanctification presented to us in context in the New Testament.
In some cases, we find that sanctification has a “provisional” meaning, such as in these passages: I Corinthians 7:14 (keep in mind that “holy” and “sanctified” are from the same Greek root) and Hebrews 10:29. It seems clear that a person doesn’t need to be a believer at all to be sanctified in this way, and the effect of such a sanctification may be temporary and based on a particular outward relationship a person has been brought into. Such an external relationship with a parent or with the Christian testimony carries with it much privilege, because it brings a man, woman, or child into a realm where Christ is honored and where the Word of God is taught. But oh, the responsibility laid upon such as these who are provisionally sanctified, lest they despise that privilege!
There is also what may be called either “progressive” or “practical” sanctification, depending upon the aspect we may want to emphasize. This aspect of sanctification is true only of real believers, for it refers to the work of God by His Spirit within Christians to progressively bring about conformity to Christ and separation from evil (II Corinthians 3:18; 7:1). We see the practical nature of this sanctification, this setting apart for God’s purposes in this evil world, in the prayer of the Lord Jesus to His “Holy Father” in John 17:17: “Sanctify them through Thy truth: Thy word is truth.” Paul’s declaration to the Thessalonian saints leaves no doubt as to the importance God places on this practical sanctification: “This is the will of God, even your sanctification” (I Thess. 4:3).
But there is a “positional” or “perpetual” (permanent) aspect of sanctification that is true of every believer in Jesus whose sins are gone because He bore them in His body on the cross (Hebrews 9:24-28; 10:10, 14). This sanctification has nothing to do with the practical sanctification described above, except that both are limited to real believers. For how could the words “once for all” or “perfected in perpetuity” (Darby’s New Translation) have any degrees or conditions attached to them other than the perfection of the completed work of Christ? As certain as the Lord Jesus Christ has gone to heaven and will never return as an offering for sin, so certain may His “sanctified” ones be (sanctified ones are “saints”) that all their sins are gone from before the eyes of a thrice-holy God. We who are sanctified in this aspect are “all of one” [kind] with Jesus! (Hebrews 2:11) And if any man sins as a saint, “we have an advocate with the Father (as His child, rather than with God as judge), Jesus Christ the righteous,” who has once for all reconciled us to God (I John 2:1; Romans 5:10-11).
Read these portions and worship, dear saint of God; you may enjoy a permanent sanctification that doesn’t depend upon you.