In the traditional Roman Divine Office, the only Hours which change their Psalms according to the specific feast day are Matins and Vespers. [1] On the majority of feasts, the first four Psalms of Vespers (109-112) are taken from Sunday, but Psalm 113, the fifth and longest of Sunday, is substituted by another; on the feasts of martyrs, by Psalm 115, on those of bishops by 131, etc. There are, however, four occasions on which Psalm 113 is not replaced, three of which are very ancient indeed, and the fourth relatively recent in origin.The three ancient feasts are Easter, Pentecost
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