Council of Chalcedon, Canon XXV

Forasmuch as certain of the metropolitans, as we have heard, neglect the flocks committed to them, and delay the ordinations of bishops the holy Synod has decided that the ordinations of bishops shall take place within three months, unless an inevitable necessity should some time require the term of delay to be prolonged.  And if he shall not do this, he shall be liable to ecclesiastical penalties, and the income of the widowed church shall be kept safe by the steward of the same Church.

Translation: Henry R. Percival, The Seven Ecumenical Councils, NPNF II.14 (1900), via CCEL.