Canon 75
That an accusation against a bishop can only be accepted from 2 or 3 witnesses from the faithful.
A heretic should not be allowed to testify against a bishop, but neither should one who is faithful be allowed to testify: By the mouth of two or three witnesses every word will be confirmed.
Greek original
Εἰς μαρτυρίαν τὴν κατὰ ἐπισκόπου αἱρετικὸν μὴ προσδέχεσθαι, ἀλλὰ μηδὲ πιστὸν ἕνα μόνον. Ἐπὶ στόματος γὰρ δύο, ἢ τριῶν μαρτύρων, σταθήσεται πᾶν ῥῆμα.
Parallel canons
IВс.2IIВс.6Карф.59131132Феоф.9