Canon XIII.
Canons of Local Councils Received in Trullo (Sardica, Carthage) · The Seven Holy Ecumenical Councils
That a bishop should not be ordained except by many bishops, but if there should be necessity he may be ordained by three.
LocalT 2.17.2
Bishop Aurelius said: What says your holiness on this matter? By all the bishops it was answered: The decrees of the ancients must be observed by us, to wit, that without the consent of the Primate of any province even many bishops assembled together should not lightly presume to ordain a bishop. But should there be a necessity, at his bidding, three bishops should ordain him in any place they happen to be, and if anyone contrary to his profession and subscription shall come into any place he shall thereby deprive himself of his honour.
LocalT 2.17.3
At the bidding of the Primate even three bishops can make a bishop. But whoever goes counter to his profession, and subscription, is deprived of his honour by his own judgment.
LocalT 2.17.6