Following in every way the decrees of the holy fathers and recognising the canon which has recently been read out—the canon of the 150 most devout bishops who assembled in the time of the great Theodosius of pious memory, then emperor, in imperial Constantinople, new Rome—we issue the same decree and resolution concerning the prerogatives of the most holy church of the same Constantinople, new Rome. The fathers rightly accorded prerogatives to the see of older Rome, since that is an imperial city; and moved by the same purpose the 150 most devout bishops apportioned equal prerogatives to the most holy see of new Rome, reasonably judging that the city which is honoured by the imperial power and senate and enjoying privileges equalling older imperial Rome, should also be elevated to her level in ecclesiastical affairs and take second place after her. The metropolitans of the dioceses of Pontus, Asia and Thrace, but only these, as well as the bishops of these dioceses who work among non-Greeks, are to be ordained by the aforesaid most holy see of the most holy church in Constantinople. That is, each metropolitan of the aforesaid dioceses along with the bishops of the province ordain the bishops of the province, as has been declared in the divine canons; but the metropolitans of the aforesaid dioceses, as has been said, are to be ordained by the archbishop of Constantinople, once agreement has been reached by vote in the usual way and has been reported to him.
Canon 28 of the Council of Chalcedon, 451 AD