What does the Bible mean when it calls something sanctified?

from the old testament

• In the Old Testament, sanctification described the setting apart of objects, places, or people for God’s service. For instance, the tabernacle and its furnishings were sanctified to be used only in worship. God told Moses, “Then you shall take the anointing oil and anoint the tabernacle and all that is in it, and consecrate it and all its furniture, so that it may become holy” (Exodus 40:9). The anointing was done to symbolize that the tabernacle and everything in it was being set side, that is, being considered holy. This meant that those objects were no longer allowed for common use, being dedicated exclusively to God.
• Not only were things sanctified, priests were also sanctified before they could serve. This meant that they were separated from ordinary life so that they could represent the people before God (Exodus 28:41; Leviticus 8:30). Setting the priests apart from the other people was necessary because God is holy and only those things which are holy could be near Him.
• Even time could be sanctified: “God blessed the seventh day and made it holy, because on it God rested from all his work that he had done in creation” (Genesis 2:3; cf., Exodus 20:8–11). By doing this, God was saying that one day a week was to be set aside for worshiping Him and resting like He did (i.e., Exodus 31:13).
• Additionally, all of Israel was set apart as a witness to the surrounding nations. God said that “if you will indeed obey my voice and keep my covenant, you shall be my treasured possession among all peoples, for all the earth is mine; and you shall be to me a kingdom of priests and a holy nation” (Exodus 19:5–6). He was not saying that each individual Israelite was holy in the way priests were sanctified, but that, as a nation, God had set aside Israel as belonging to Him and, thus, with a distinct relationship to Him.

from the new testament

• All believers in Christ are set apart. At conversion, we are sanctified once for all by the work of Christ’s sacrifice. This is what Paul meant when he said, “you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God” (1 Corinthians 6:11). He was talking about a past, decisive act where believers were set apart to serve God. Notice that this is possible because Jesus lived perfectly and His righteousness (His holiness) is credited to Christians by faith (Philippians 3:9).
• Because the believer’s position is based on Jesus’ righteousness, the believer has much room to grow to be actually holy. Therefore, while counted as sanctified, sanctification is also ongoing as the Spirit works in believers, transforming their lives to reflect Christ’s holiness. Paul said, “For just as you once presented your members as slaves to impurity and to lawlessness leading to more lawlessness, so now present your members as slaves to righteousness leading to sanctification” (Romans 6:19). He was saying that after a believer is saved, he or she is expected to strive to grow in righteousness.
• At the same time, perfect sanctification is a future goal. Paul prayed, “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. He who calls you is faithful; he will surely do it” (1 Thessalonians 5:23–24). God has promised that all believers will be perfect after this life, once believers are free from sin’s presence and have seen Jesus (1 John 3:2).
• Jesus Himself is central to sanctification. He said, “for their sake I consecrate myself, that they also may be sanctified in truth” (John 17:19). The word “consecrate” is a form of the same Greek word translated as “sanctified” later in the verse. Jesus was saying that He set Himself apart to accomplish the Father’s will, so that His people would be able to be set apart to serve God. To be sanctified, then, means to be set apart through the work of Jesus on the cross.

implications for today

To say that something or someone is sanctified is to acknowledge God’s ownership of that thing or person. If you are in Christ, your life is no longer your own. You have been set apart by being cleansed from your sin through Jesus and are now called to live for Him. Everything in your life, your decisions, your relationships, your work, are all to be done as His servant. Whatever you do, you are to display His holiness.

What if you keep failing and don’t feel like you are living up to your calling as sanctified? The reality is that no believer lives up to it. Remember that you were set apart because of what Jesus did, and not because of what you do. You should be battling against your sin because that is part of God’s ongoing work to make you holy. If you are, allow that fight to give you assurance! God counts you as perfectly righteous because of what Jesus did, and He is now progressively sanctifying you so that you will become like Jesus. Rest assured that God will complete what He began in you (Philippians 1:6; 2:12–13).

That said, do not be satisfied to simply be called set apart—live out that calling. That is, strive to obey God in your life (Ephesians 4:1–32). God set you apart so that the rest of the world might come to know Him as well (John 17:17–21). So, in your home, workplace, or school, allow your ever growing, sanctified life be a testimony that you serve the Lord and exist for His glory.