The term “sanctify” is used many times in the KJV Bible…
1. Old Testament word: “qadash” means “to make clean, holy, to hallow, to separate”
2. New Testament word: “hagiazo” means to dedicate, purify, consecrate
The idea is this… “sanctify” means to separate for the use of God. It speaks of separation from sin to God, to purify from sin, to dedicate to God’s use.
Here are a few samples of Biblical usage….
This term is used to describe an attribute of the Christ, Who is totally separated from sin to be perfectly used by the Father:
Say ye of him, whom the Father hath sanctified, and sent into the world, Thou blasphemest; because I said, I am the Son of God?
This term also speaks of an attribute that is given to saints through the work of Christ on the cross:
And base things of the world, and things which are despised, hath God chosen, [yea], and things which are not, to bring to nought things that are: That no flesh should glory in his presence. But of him are ye in Christ Jesus, who of God is made unto us wisdom, and righteousness, and sanctification, and redemption: That, according as it is written, He that glorieth, let him glory in the Lord. (1 Corinthians 1:28-31)
It also describes an ongoing process of spiritual growth, separation from sin and greater service for Him:
Sanctify them through thy truth: thy word is truth. As thou hast sent me into the world, even so have I also sent them into the world. And for their sakes I sanctify myself, that they also might be sanctified through the truth. (John 17:17-19)