We believe that God is present everywhere and that the eyes of the Lord in every place behold the good and the evil;1 but let us especially believe this without any doubt when we are assisting at the Divine Office. Therefore let us ever remember the words of the prophet: Serve ye the Lord in fear;2 and again, Sing ye wisely;3 and, I will sing to thee in the sight of the angels.4 Let us then consider how we ought to behave ourselves in the presence of God and his angels, and so sing the psalms that mind and voice may be in harmony.
1Prov xv,3
2Ps ii, 11
3Ps xivi, 8
4Ps cxxxvii,1