THOU, HOWEVER, O LORD, HAVE MERCY ON US.
— With these words, to which the choir responds “Deo gratias,” the reader concludes the individual lessons of the Divine Office and the readings in the refectory, already in use by the 8th century (Ordo Romanus XIX, 13 [ed. Andrieu]).
To finish the more extended reading of the Office, the superior first gave a sign, a knock on the table (loc. cit., 11; Charlemagne is said to have given the signal “baculo aut sono gutturis”), or, according to the Ordines Romani XI, 8, and XIII, 14 (ed. Mabillon), the deacon would remind the reader of the first words “Tu autem,” and the reader would continue by repeating them and saying the entire verse. Therefore, after “Tu autem” there is no understood ellipsis of words such as “cessa,” “desine,” or similar. Besides the T. a., other concluding formulas were also in use, as is still the case in the first Nocturn of the Sacred Triduum after the Lamentations of Jeremiah: “Jerusalem, Jerusalem, convertere ad Dominum Deum tuum,” or after the reading of the prophets: “Haec dicit Dominus...,” or after that of the Apostle: “in Christo Jesu Domino nostro,” etc. The short chapters of Vespers, Lauds, and the minor Hours, since they were originally fixed and recited from memory, do not end with the T. a., but are followed by “Deo gratias.”
The T. a. is explained as a plea for God’s mercy for any defects during the reading or, better, as a prayer to obtain the fruits of the reading. Analogously to this final thanksgiving of the reading, a blessing is given to the reader beforehand.
As St. Benedict notes (Rule, chaps. 9 and 11), the reader receives from the superior a blessing or some kind of authorization, requested with the formula “Jube, domne, benedicere,” “Benedic pater,” or similar, a blessing already used by St. Ambrose. There are a great variety of forms for this blessing. Even the bishop or the pope, before reading, asks for the blessing with “Jube, Domine, benedicere,” addressing the