“Sanctification” — and the related words “sanctify” and “sanctified” — are religious sounding words which we have heard but perhaps do not clearly understand.  What does the Bible mean when it uses these words?  Let’s take a look.

The Hebrew word translated sanctify is qadash, which has quite a broad range of meanings: to consecrate, sanctify, dedicate, be holy, be separate.  It is closely related to the Hebrew word qodesh, which means: holy, sacred, separateness.

Qodesh has a narrower meaning and relates to God and His holiness.

Qadash is something that both God and men can do to both men and objects.  Here are some examples which make this clearer.

God sanctified the seventh day (the Sabbath).

Gen 2:3  Then God blessed the seventh day and sanctified [qadash] it, because in it He rested from all His work which God had created and made.

Sanctifying the Sabbath is also something that men can do.

Neh 13:22  And I commanded the Levites that they should cleanse themselves, and that they should go and guard the gates, to sanctify [qadash] the Sabbath day. Remember me, O my God, concerning this also, and spare me according to the greatness of Your mercy!

God sanctifies people.

Exo 31:12  And the LORD spoke to Moses, saying,
Exo 31:13  “Speak also to the children of Israel, saying: ‘Surely My Sabbaths you shall keep, for it is a sign between Me and you throughout your generations, that you may know that I am the LORD who sanctifies [qadash] you.

Lev 20:8  And you shall keep My statutes, and perform them: I am the LORD who sanctifies [qadash] you.

Moses sanctified the people, and later Joshua told the people to sanctify themselves.

Exo 19:14  So Moses went down from the mountain to the people and sanctified [qadash] the people, and they washed their clothes.

Jos 3:5  And Joshua said to the people, “Sanctify [qadash] yourselves, for tomorrow the LORD will do wonders among you.”

God sanctified the tabernacle (which contained the altar) by His glory.

Exo 29:43  And there I will meet with the children of Israel, and the tabernacle shall be sanctified [qadash] by My glory.

The priests were commanded to sanctify the altar.

Exo 29:36  And you shall offer a bull every day as a sin offering for atonement. You shall cleanse the altar when you make atonement for it, and you shall anoint it to sanctify [qadash] it.
Exo 29:37  Seven days you shall make atonement for the altar and sanctify [qadash] it. And the altar shall be most holy. Whatever touches the altar must be holy.

The Greek word translated sanctify is hagiazo, which means: to make holy, purify, consecrate.  It is closely related to the Greek word hagiasmos, which means: sanctification, purification, consecration.  The Greek hagiazo is closer in meaning to the Hebrew qodesh than qadash.  This means (in most English translations of the Bible), “sanctify” in the New Testament exclusively means “make holy”, whereas “sanctify” in the Old Testament can mean “make holy” or “separate, set apart”.

Sanctification is an extremely important process, which is part of salvation. 

God sanctifies us, makes us holy, by His truth.

Joh 17:17  Sanctify [hagiazo] them by Your truth. Your word is truth.
Joh 17:18  As You sent Me into the world, I also have sent them into the world.
Joh 17:19  And for their sakes I sanctify [hagiazo] Myself, that they also may be sanctified [hagiazo] by the truth.

1Th 5:23  Now may the God of peace Himself sanctify [hagiazo] you completely; and may your whole spirit, soul, and body be preserved blameless at the coming of our Lord Jesus Christ.

We are also sanctified in Christ Jesus through His shed blood.

1Co 1:2  To the church of God which is at Corinth, to those who are sanctified [hagiazo] in Christ Jesus, called to be saints, with all who in every place call on the name of Jesus Christ our Lord, both theirs and ours:

Heb 10:9  then He said, “BEHOLD, I HAVE COME TO DO YOUR WILL, O GOD.” He takes away the first that He may establish the second.
Heb 10:10  By that will we have been sanctified [hagiazo] through the offering of the body of Jesus Christ once for all.

Heb 13:12  Therefore Jesus also, that He might sanctify [hagiazo] the people with His own blood, suffered outside the gate.

Conclusion

In the Old Testament, sanctify has a broader meaning than In the New Testament.  Sanctify in the Old Testament means to make holy or to set apart.  Sanctify in the New Testament means to make holy.  God sanctifies us through His truth and by Christ’s shed blood.