WHAT DO THE WORDS "SANCTIFY" AND SANCTIFICATION" MEAN? My English dictionary will give a good definition of sanctification. But biblical terms should always be defined by their usage in the Word of God. So we should look to the Bible to see what these terms mean. The word "sanctify is used three ways in the Word of God. First, it means "to set apart," particularly TO SET APART FOR GOD OR FOR DIVINE SERVICE. Sanctification is taking something that is common and ordinary and setting it apart for God, separating it unto the service of God. This is the primary meaning of the word "sanctify" as is used in the Bible. The seventh day (Gen. 2:3), the firstborn of Israel (Ex. 13:2), the tabernacle (Ex. 29:44), and the Lord Jesus Christ himself (John 10:16; 17:19) were all sanctified in this sense.
Second, that which is sanctified is REGUARDED AND TREATED AS HOLY, AND DECLARED TO BE HOLY. For example God himself is said to be sanctified by his people (Isa. 8:13; Lev. 10:3; Num. 20:12; Matt. 6:9). When we sanctify the Lord God in our hearts, we do not change him. We simply regard and reverence him as the holy Lord God.
Third, to sanctify is TO CLEANSE, WASH; PURIFY, AND MAKE HOLY. Ceremonially, this was done when God came down among his people (Ex. 19:10-11; Josh. 3:5). Their washing, their purification was typical of the believer's sanctification by the Spirit.
THIS IS HOW GOD'S ELECT ARE SAID TO BE SANCTIFIED IN THE BIBLE.