To “sanctify” something is to set it apart for special use.

Gen 2:3

And God blessed the seventh day, and sanctified it:

Exo 19:10

And the LORD said unto Moses, Go unto the people, and sanctify them

Lev 20:7

Sanctify yourselves therefore, and be ye holy: for I am the LORD your God.

John 17:17

Sanctify them through thy truth: thy word is truth.

1 Cor 6:11

And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.

Eph 5:26

That he might sanctify and cleanse it with the washing of water by the word,

2 Th 2:13

But we are bound to give thanks alway to God for you, brethren beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and belief of the truth:

2 Tim 2:21

If a man therefore purge himself from these, he shall be a vessel unto honour, sanctified,

Heb 9:13-14

How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?