Council of Chalcedon
Council of Chalcedon, Canon XXI
Definition of faith and received canons; reception qualifications retained; not the full proceedings
Canon XXI
Clergymen and laymen bringing charges against bishops or clergymen are not to be received loosely and without examination, as accusers, but their own character shall first be investigated.
Translation: Henry R. Percival, The Seven Ecumenical Councils, NPNF II.14 (1900), via CCEL.
Source: Council of Chalcedon (CCEL)