Using the word sanctify in the sense of purify or cleanse from sin in God’s sight, the apostle Paul wrote: “For if the blood of goats and of bulls and the ashes of a heifer sprinkled on those who have been defiled sanctifies to the extent of cleanness of the flesh, how much more will the blood of the Christ, who through an everlasting spirit offered himself without blemish to God, cleanse our consciences from dead works that we may render sacred service to the living God?”​—Heb 9:13, 14.

“The blood of the Christ” signifies the value of his perfect human life; and it is this that washes away the guilt of sin of the person believing in him. Hence it really (not just typically [compare Heb 10:1-4]) sanctifies to the purifying of the believer’s flesh, from God’s standpoint, so that the believer has a clean conscience.

God’s Word and spirit. God’s Word plays a great part in sanctification, and it must be followed closely for sanctification to be maintained. (Ac 20:32) To the believer and sanctified one, God also sends his holy spirit, which is a strong force working in him for cleanness. It helps the sanctified one to be obedient, keeping him in a clean way of life. (1Pe 1:2) Guidance by God’s spirit makes it possible for the offering of such ones to be sanctified, clean, acceptable to God. (Ro 15:16)