The Rule of St. Benedict - Chapter 47. Announcing The Hours For The Work Of God

(1) It is the abbot's care to announce, day and night, the hour for the Work of God. He may do so personally or delegate the responsibility to a conscientious brother, so that everything may be done at the proper time.

(2) Only those so authorized are to lead psalms and refrains, after the abbot according to their rank.
(3) No one should presume to read or sing unless he is able to benefit the hearers; 4let this be done with humility, seriousness and reverence, and at the abbot's bidding.

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