One of the four marks by which the true Church of Jesus Christ can be recognized and distinguished from false Churches. There is no doubt that Christ intended holiness to be a note of His Church. Saint Paul writes to the Ephesians:
Christ also loved the church, and delivered himself up for it: that He might sanctify it; cleansing it by the laver of water in the word of life: That he might present it to himself, a glorious church, not having spot or wrinkle, or any such thing, but that it should be holy, and without blemish. (Ephesians 5)