From the Breviary according to the use of the Roman Curia, 1529, the continuation of the sermon for the second day in the Octave of All Saints.
Since the fall of the holy Angels was to be made good by their dealings with men, and for this reason they rejoice in the conversion of sinners, longing for the salvation of men, and willingly submit themselves to the will (of men), we must likewise raise our prayers up to them. Oh! if someone had his eyes open, as the prophet by praying opened up those of his servant (4 Kings 6, 17-20), he would see how princes go forth joined with singers (Psalm 67, 26), he would see with what care and solemnity they dance among them, are present to their prayers, are in the midst of their meditations, surround them as they rest, guide those that rule and serve. Therefore, since we know that they so graciously visit those who lie in dung and mud, and joyfully gather them into the heavenly fatherland, it is worthy that we strive to invite them to the joy of our solemnity.This somewhat opaque passage seems to require a brief translator’s note, since the very clever rhetoric of the Latin original does not translate well into English. The words of Psalm 67, “Praevenerunt principes conjuncti psallentibus – Princes went before joined with singers ” are understood to mean Angels joined to the choirs of men as the latter sing God’s praises. In Latin, each of the verbs that follows, describing the actions of the Angels (“they dance… guide them”) is a compound of the verb “esse – to be”: “intersint cantantibus, adsint orationibus, insint meditantibus, supersint quiescentibus, ordinantibus et procurantibus praesint.” This beautifully expresses the idea that in every aspect of our religious life, we accompanied by the presence of the Holy Angels.
The Cantoria, or Cantor's Gallery of Florence Cathedral, by Luca della Robbia, 1431-38, now kept in the Cathedral Museum. The psalm written out above and below the panels of singers and musicians is Psalm 150, formerly sung every day at Lauds with Psalms 148 and 149. As currently displayed, the eight panels are copies; the originals have been detached for easier viewing and are displayed on the wall below the Cantoria itself, as seen at this website.