"And God blessed the seventh day, and sanctified it: because that in it He had rested from all His work which God created and made" (Genesis 2:3).
The Biblical doctrine of sanctification has long been controversial and often seems difficult to comprehend. But it is not a condition of super-spirituality which only very special saints can achieve, although many think of it that way.
It may be surprising that the term applied not only to certain people, but also to special things or events. The very first use of the term (and thus an important defining usage) is in our text, and refers to setting apart a regular day of the week. That is God sanctified the day on which He rested from His great work of creation.
It is also translated in various other ways, especially dedicated or consecrated. The basic meaning seems to be set apart for use in God's service.
Thus, with particular reference to Christians, we are exhorted by Paul to "depart from iniquity" and thus to be "a vessel unto honor, sanctified, and meet for the master's use, and prepared unto every good work" (II Timothy 2:19,21). We cannot do this without divine guidance and help, of course. Jesus prayed: "Sanctify them through thy truth: thy word is truth" (John 17:17). In fact, we have been "chosen . . . to salvation through sanctification of the Spirit and belief of the truth" (II Thessalonians 2:13).
In a vital sense, every sincere believer has really been set apart to God because Christ Himself is "made unto us
. . . sanctification, and redemption" (I Corinthians 1:30). Thus all genuine Christians are actually "saints" (which comes from a closely related Greek word). We do need to recognize that we have indeed been "set apart" for God and thus should always think and behave "as becometh saints" (Ephesians 5:3). HMM