« MIRIS MODIS REPENTE LIBER, FERREA ». – Hymn of Vespers for the feast of s. Pietro in Vincoli. It consists of a single stanza taken from the hymn Felix per omne festum mundi cardines, attributed to Elpidia or, more likely, to s. Paolino d'Aquileia.
The first two verses are a paraphrase of the account of the liberation of s. Pietro (v. Act. 12:6–11), commemorated on this day, when the dedication of the Basilica of S. Pietro in Vincoli, erected by Eudossia on the Esquiline, is celebrated; the other three draw inspiration from Jesus’ command to Pietro to feed his sheep and his lambs (Io. 21:15–17).
BIBL.: C. Albini, La poésie du Bréviaire, Lione s. a., pp. 318–319; G. G. Belli, Gli inni del Breviario tradotti, Roma 1856, pp. 290–91; A. Mirra, Gli inni del Breviario romano, Napoli 1947, p. 230.