Правило 20
On the prohibition of kneeling on Sundays and on all days of Pentecost.
Since some kneel on Sunday and on the days of Pentecost, in order for everything to be observed equally in each episcopal region, it pleased the Holy Council that prayers be offered to God while standing.
Greek original
Ἐπειδή τινές εἰσιν ἐν τῇ Κυριακῇ γόνυ κλίνοντες, καὶ ἐν ταῖς τῆς Πεντηκοστῆς ἡμέραις· ὑπὲρ τοῦ πάντα ἐν πάσῃ παροικίᾳ ὁμοίως παραφυλάττεσθαι, ἑστῶτας ἔδοξε τῇ ἁγίᾳ συνόδῳ τὰς εὐχὰς ἀποδιδόναι τῷ Θεῷ.
Parallel canons
Ап.66Трул.6690Гангр.18Петра15Вас.91Феоф.1