To sanctify means to set apart as holy and consecrated to God. It carries three overlapping senses in Scripture: (1) Positional — the believer is already sanctified through Christ's blood, set apart as God's own (1 Corinthians 6:11, Hebrews 10:10); (2) Progressive — the ongoing work of the Holy Spirit conforming the believer to Christ's image (1 Thessalonians 5:23, 2 Corinthians 3:18); (3) Final — the completed sanctification at glorification. God sanctifies people, places, and times: the Sabbath (Genesis 2:3), the tabernacle (Exodus 40:9), and His people (John 17:17). The instrument of progressive sanctification is the Word: "Sanctify them in the truth; your word is truth" (John 17:17).
SANCTIFY, v.t. 1. To separate, set apart, or appoint to a holy, sacred, or religious use. 2. To purify; to cleanse from sin; to make holy by detaching the affections from the world and its defilements, and exalting them to a supreme love to God. 3. To make the means of holiness; to render productive of holiness or piety. 4. To hallow; to secure from violation. 5. To free from sin; applied to the blood of Christ.
Modern Christianity has largely reduced sanctification to a mood — a vague aspiration toward being "a better person." The rigorous, costly nature of progressive sanctification — the mortification of sin (Colossians 3:5), the renewing of the mind (Romans 12:2), the striving for holiness (Hebrews 12:14) — has been replaced by therapeutic self-improvement language. Meanwhile, "sanctified" has been co-opted by secular culture to mean "approved" or "given a pass" ("the ends sanctify the means"). True sanctification is Spirit-driven, Word-fueled, death-dealing to the flesh, and relentlessly God-directed — not a soft self-help process.
John 17:17 — "Sanctify them in the truth; your word is truth."
1 Thessalonians 5:23 — "Now may the God of peace himself sanctify you completely, and may your whole spirit and soul and body be kept blameless at the coming of our Lord Jesus Christ."
Hebrews 10:10 — "And by that will we have been sanctified through the offering of the body of Jesus Christ once for all."
Hebrews 12:14 — "Strive for peace with everyone, and for the holiness without which no one will see the Lord."
1 Corinthians 6:11 — "But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God."
H6942 — קָדַשׁ (qadash): "to be holy, consecrate, sanctify" — to separate to God and His purposes
G37 — ἁγιάζω (hagiazō): "to sanctify, make holy, consecrate, purify" — used in John 17:17 and Hebrews 10:10
G40 — ἅγιος (hagios): "holy, set apart, sacred" — the root from which sanctify is derived
"God does not sanctify you because you've earned it — He sets you apart by His own declaration, then spends a lifetime conforming your life to that declaration."
"The Word of God is not just information; it is the instrument Jesus specifically chose to sanctify His people: 'Your word is truth.'"
"You cannot sanctify yourself any more than a dirty cloth can wash itself clean — the work is God's, but the cooperation is yours: 'Work out your salvation with fear and trembling, for it is God who works in you.'"