Правило 55
A reminder to the Roman Church about the prohibition of fasting on the Saturday of Pentecost.
Since we learned that the inhabitants of the city of Rome fast on Saturdays during the holy fast of Pentecost, contrary to Church Tradition, the Holy Council decided that the Roman Church should also inviolably observe the rule that says: “If any cleric is found to fast on the Lord's Day or on Saturday (with the exception of only one Saturday), he will be deposed. And if he is a layman, then let him be excommunicated.”
Greek original
Ἐπειδὴ μεμαθήκαμεν, τοὺς ἐν τῇ Ῥωμαίων πόλει, ἐν ταῖς ἁγίαις τῆς Τεσσαρακοστῆς νηστείαις, τοῖς ταύτης σάββασι νηστεύειν, παρὰ τὴν παραδοθεῖσαν ἐκκλησιαστικὴν ἀκολουθίαν· ἔδοξε τῇ ἁγίᾳ συνόδῳ, ὥστε κρατεῖν καὶ ἐπὶ τῇ Ῥωμαίων ἐκκλησίᾳ ἀπαρασαλεύτως τὸν κανόνα, τὸν λέγοντα· Εἴ τις κληρικὸς εὑρεθείη τὴν ἁγίαν Κυριακὴν νηστεύων, ἢ τὸ σάββατον, πλὴν τοῦ ἑνὸς καὶ μόνου, καθαιρείσθω· εἰ δὲ λαϊκός, ἀφοριζέσθω.
Parallel canons
Ап.66