Ap. Can. xiii. 14: “It is clear from the Philosophumena of Hippolytus (ix. 12) that by the beginning of the 3d century the rule of monogamy for the clergy was well established, since he complains that in the days of Callistus ‘digamist and trigamist bishops, and priests and deacons, began to be admitted into the clergy.’ Tertullian recognises the rule as to the clergy. Thus in his De Exhortatione Castitatis (c. 7) he asks scornfully; ‘Being a digamist, dost thou baptize? Dost thou make the offering?’” Dict. C. A. i. 552. Vide also Canon Bright, Notes on the Canons of the first four General Councils. On Can. Nic. viii. p. 27.