St. Augustine
the Rule

Chapter II

2.1 Be assiduous in prayer [4], at the hours and times appointed.

2.2 In the Oratory no one should do anything other than that for which was intended and from which it also takes its name. Consequently, if there are some who might wish to pray there during their free time, even outside the hours appointed, they should not be hindered by those who think something else must be done there.

2.3 When you pray to God in Psalms and hymns [5], think over in your hearts the words that come from your lips.

2.4 Chant only what is prescribed for chant; moreover, let nothing be chanted unless it is so prescribed.