Separation from ordinary use to a sacred purpose. The Hebrew word קָדֵשׁ and the Greek word ἃγιος, rendered "holy," "hallowed," and "sanctified," are applied to certain times which were hallowed — as the Sabbath and the Hebrew festivals (Genesis 2:3; Exodus 20:8; Exodus 20:11; Leviticus 23:37; 2 Kings 10:20); to the things said to be hallowed, as the sacred incense or perfume (Exodus 30:36; Matthew 7:6), the sacred vestments (Exodus 28:2; Exodus 28:4), the sacred utensils (Exodus 30:29; 1 Chronicles 22:10; 2 Timothy 2:21), the holy bread (Leviticus 21:22; 1 Samuel 21:5), the altar (Exodus 29:37; Exodus 30:1; Exodus 30:10; Matthew 23:19), and portions of the sacrifices (Leviticus 2:3; Leviticus 2:10). So, also, of places said to be hallowed (Exodus 3:5; Acts 7:33), as the holy city, i.e. Jerusalem (Nehemiah 11:1; Isaiah 48:2; Matthew 4:5; Matthew 24:15; Matthew 27:53; Acts 6:13; Acts 22:28), the holy mountain, i.e. Zion (Psalms 2:6), the Tabernacle (Numbers 18:10); the Temple (Psalms 138:2), the most holy place, the oracle (Exodus 26:33; Exodus 28:43; Hebrews 9:2-3; Hebrews 9:12; 1 Kings 6:16; 1 Kings 8:6; Ezekiel 41:23). So, also, men are said to be hallowed, as Aaron and his sons (1 Chronicles 23:13; 1 Chronicles 24:5; Isaiah 43:28), the firstborn (Exodus 13:2), and the Hebrew people (Exodus 19:10; Exodus 19:14; Daniel 12), also the pious Hebrews, the "saints" (Deuteronomy 33:3; Psalms 16:3; Daniel 7:18), like the word חָסַיד, rendered "saint" (Psalms 30:4; Psalms 31:23; Psalms 37:28; Psalms 1:5; Psalms 52:9; Psalms 79:2; Psalms 97:10), and "godly" (Psalms 4:3).
The terms are also used of those who were ceremonially purified under the Mosaic law (Numbers 6:11; Leviticus 22:16; Leviticus 22:32; Hebrews 9:13). But, though the external purifications of the Hebrews, when any one had transgressed, had to do with restoration to civil and national privileges, they did not necessarily induce moral and spiritual holiness. They, however, reminded the sincere Hebrew that he was unclean in the sight of God; and that the ceremonial cleansings, by which he had been restored to his civil and political rights, were symbols of those "good things that were to come" — spiritual and eternal salvation — which should accrue through the sprinkling of the blood of Christ and the gift of the Holy Spirit. He was thus assured that "without holiness no man shall see the Lord" (Hebrews 9:14; Hebrews 12:14). Hence, sanctification is used to designate that state of mind induced by the indwelling of the Holy Spirit, thus producing internal and external holiness (John 3:5; 1 Corinthians 6:11; Ephesians 5:26; 1 Thessalonians 4:3-4; 1 Thessalonians 4:7). It is true, sanctification is sometimes spoken of as the work of man himself (Exodus 19:22; Leviticus 11:44; Leviticus 20:7-8; 1 Peter 3:15). When a person solemnly and unreservedly gives himself to God, he then may be said to sanctify himself. He is then enabled to believe in Christ with his heart unto righteousness, and God instantly, by the communication of his Holy Spirit, sanctifies the believer. Thus the believer gives himself to God, and God, in return, gives himself to the believer (Ezekiel 36:25-29; 1 Corinthians 3:16-17; 1 Corinthians 6:19; 2 Corinthians 6:16-18; Ephesians 2:22). This sanctification, which is received by faith, is the work of God within us.
In a general sense, "sanctification" comprehends the whole Christian life (Galatians 5:22-23; 1 Peter 1:15-16; 1 Peter 1:22; Hebrews 12:10; James 4:8). In 1 Thessalonians 5:23, the apostle prays for the sanctification of the entire Church in all its various departments. In 1 Corinthians 7:14, it is said, the unbelieving husband, or wife, is "sanctified" — that is, to be regarded not as unclean, but as specially claiming the attention of the Christian community. The term "sanctified" is also used in the sense of expiation (Hebrews 10:10; Hebrews 10:14; Hebrews 10:29). See Hagenbach, Hist. of Doctrines, 2, 281, 288, 503; Oosterzee, Christian Dogmatics. (See HOLINESS).