Rule of St Benedict for the day

Let there be said the verse: Deus in adjutorium meum intende, Domine ad adjuvandum me festina,¹ and Gloria; then the hymn proper to each Hour. Then at Prime on Sunday, four sections of the hundred and eighteenth psalm; and at each of the remaining hours, that is Terce, Sext and None, three sections of the same hundred and eighteenth psalm. At Prime on Monday let three psalms be said, namely the first, second and sixth. And so at Prime every day until Sunday let there be said three psalms taken in their order up to the nineteenth; but let the ninth and seventeenth be each divided into two. Thus it comes about that the Night Office on Sundays always begins with the twentieth psalm.