Правило 49
The command to perform the Sacrament of the Eucharist during Great Lent only on Saturdays and Sundays.
About the fact that Bread should not be brought on Lent, with the exception of Saturday and Sunday.
Greek original
Ὅτι οὐ δεῖ ἐν τῇ Τεσσαρακοστῇ ἄρτον προσφέρειν, εἰ μὴ ἐν Σαββάτῳ καὶ Κυριακῇ μόνον.
Parallel canons
Ап.6669Трул.52Лаод.505152