The word “holy” is used in connection with days, persons and things. Holy things are made so by the will of God. In other words, they are set apart for God by Himself. These holy things are for this reason to be sanctified, that is, counted as holy, by man. Thus an Israelite was to sanctify, or keep holy, the seventh day, not to make it holy, but because God had made it so.
If we have come to Jesus as the sin offering, if we have by faith touched Him, so as to be made whole, that touch has brought us into a holy relationship with God, having now the holy life of Christ and the Holy Spirit dwelling in us.
Have we received the “washing of water by the Word”? It is that we may be holy and without blemish. Do we realize this? All believers are set apart by the precious blood, by the anointing of the Holy Spirit, and by the Word which is truth. If we are saved, if we have received the Spirit of the Holy One, we are holy; we are set apart for God, now and forever — His temple, His people, the bride of His Son. To this sanctified people it is said in the words of tender love and grace, “Be ye holy; for I am holy” (1 Peter 1:16).
Adapted from The Bible Student, Vol. 1:36