Today's feast celebrates the dedication of two great Roman Churches, each of which contains the body of the saints they are named for: the Vatican (St Peter's) and St Paul Outside-the-Walls.
At Matins the readings for Nocturn I&II are as for the weekday; the reading for Nocturn III is of the feast:
Among the holy places which have been held in honor among Christians from the beginning, one of the foremost has always been the Confession of St. Peter in the Vatican, made sacred by the tomb of the Prince of the Apostles. Here Constantine the Great is said to have prostrated himself on the ground and, with pick and shovel, to have marked but the place for the basilica, which he built at his own expense. This basilica was dedicated on November 18 by Pope St Sylvester. It was at that time that he decreed that henceforth altars were to be made only of stone. Eventually, having deteriorated with age this basilica was rebuilt from its foundations with greater magnificence. The loving care of several successive popes saw to the long task of rebuilding, and in 1626 Pope Urban VIII solemnly dedicated the new basilica on the anniversary of the original dedication. In the same way, the basilica of St. Paul on the Ostian Way was very richly built by Emperor Constantine and consecrated by St. Sylvester. Then, after it had been destroyed by a great fire, it was rebuilt more splendidly than before by the untiring devotion of four popes. And Pius IX, surrounded by a solemn assembly of bishops, consecrated it on the auspicious occasion of the definition of the dogma of the Immaculate Conception of the Blessed Virgin Mary.