Правило 51
On the prohibition of celebrating martyrs during Great Lent, with the exception of Saturdays and Sundays.
That we should not celebrate the birthdays (γενέθλια) of martyrs on Lent, but that we should commemorate the holy martyrs on Saturdays and Sundays.
Greek original
Ὅτι οὐ δεῖ ἐν τῇ Τεσσαρακοστῇ μαρτύρων γενέθλια ἐπιτελεῖν, ἀλλὰ τῶν ἁγίων μαρτύρων μνήμας ποιεῖν ἐν τοῖς σαββάτοις καὶ ταῖς Κυριακαῖς.
Parallel canons
Ап.6669Трул.52Лаод.495052