Invitatory. Venite Adoremus....  The cry of the Church calling on all to adore and praise God, Who has done all for us, Who is the Great Shepherd, and we, the sheep of His fold, should not harden our hearts as did the ungrateful Jews.  We should pray for all, Catholics, infidels and sinners.

“A message from the saints.  Let us imagine, like St. Stephen at his martyrdom, we are privileged to see the heavens opened, and before our eyes the City of God, with its twelve gates all of pearl, and its streets of pure gold, as it were transparent glass, is laid bare, and that we see the angels in their legions, and the redeemed of the Lord around the throne of God.  Thousands of thousands are ministering to Him,” as St. John tells us, “and ten thousand times a hundred thousand stand before Him,” and we hear the voice of God, as the noise of many waters in company with that great multitude which no man can number, out of every tribe and nation, clothed in white robes, with palms in their hands, coming into Sion with praise, with everlasting joy upon their heads, for from their eyes God has wiped away all tears, and sorrow and mourning have fled away.

“There are the white-robed army of Martyrs, holy Confessors, too, men of renown in their generation, and Virgins, the Spouses of Christ:  there are those who have come through great tribulation, who once, perchance, were far from God, but have washed their robes in the blood of the Lamb and are now numbered among the people of God, sitting in the beauty of peace and in the tabernacle of confidence and in wealthy rest.  Let us bring them all before us in vision.  They have overcome the beast and are standing by the sea of glass, having the harps of God; the Prince of Pastors has appeared to them and they have received a never-failing crown of glory and by the Lamb of God they have been led to fountains of the waters of life.”  Let us listen as they sing their canticle to God, “Holy, Holy, Holy, Lord God of Hosts, who is and who was and who is to come”; let us listen as they sing to us, for we are fellow citizens with them, and where they are we also must be if we remain faithful to the end.  What do they sing, “O come let us praise the Lord with joy; let us joyfully sing to God, our Saviour” (Sing ye to the Lord, pp. 94-95—­Rev. R. Eaton).

The authorship of this psalm—­which is said daily in Matins—­is attributed to David in the Septuagint and Vulgate.  Its Latin form in the invitatory differs slightly from the Vulgate text.  The Breviary retains here the text of St. Jerome’s revision and the Vulgate contains the second and more correct revision.

Hymns.  The hymn is an answer to the invitation given to us in the invitatory, to praise God and to rejoice with Him.  It is a song of joy and praise.  Hymns were introduced into the Divine Office in the Eastern Church before the time of St. Ambrose (340-397).  To combat the Arians, who spread their errors by verse set to popular airs, St. Ambrose, it is said, introduced public liturgical hymn-singing in his church in Milan, and his example was followed gradually through the Western Church. (See Note A, infra.)