17. The opening of the doors is the ejection of sin. Rightly, therefore, doth the bishop strike three times, because that number is most known and most sacred; and in any consecration the bishop ought to smite the doors three times, because without the invocation of the Trinity, there can be no sacrament in the Church.
18. The threefold proclamation, 'Lift up your heads,' etc., signifieth the threefold power of Christ, that, namely, which He hath in heaven, and in the earth, and in hell. Whence it is said in the hymn for the Ascension, 'That the threefold frame of things, whether heavenly, earthly, or infernal, may bow the head, having been subdued. [Footnote 395]
[Footnote 395: This hymn, by S. Gregory, is used in the office of matins in the Roman Breviary.]
19. Next the bishop entereth by the open door to denote that if he duly exercise his office, nothing can resist him; according to that saying, 'Lord, who shall resist Thy power?' And he entereth, accompanied by two or three, that in the mouth of two or three witnesses every word of the consecration may stand sure. Or else because the Lord in His Transfiguration, in the presence of a few, prayed for the Church. And the bishop as he entereth saith, 'Peace be to this house and to all them that dwell therein'; because Christ entering the world made peace between God and man; for He came that He might reconcile us to God the Father.
20. After this while the Litany is being said the bishop prostrateth himself and prayeth for the sanctification of the house. For Christ also humbling Himself before His Passion prayed for His disciples and 'them that should believe through His word,' saying, 'Father, sanctify them in Thy name.' [Footnote 396] But after he hath risen up he prayeth without benediction, since he saith not 'The Lord be with you'; because the Church is not yet as it were baptised, and because Catechumens only are not worthy that this mark of approval should be given to them, since they are not yet sanctified: but nevertheless prayer is to be made for them.
[Footnote 396: S. John xvii.]
21. The clergy praying and chanting the Litany representeth the Apostles who intercede with God for the sanctification of the Church and of souls.
The alphabet is written on the pavement of the church in this manner. A cross made with ashes and sand is described athwart the church, upon which cross of dust the alphabet is written in the shape of a cross in letters of Greek and Latin, but not of Hebrew, because the Jews have departed from the faith; and it is written with the pastoral staff.