Council of Trent: Session XXIII, Reformation, Chapter XII

CHAPTER XII. Age required for the major orders; the deserving only to be admitted.

No one shall for the future be promoted to the order of subdeaconship before the twenty-second year of age; to that of deaconship before his twenty-third year; to that of priesthood before his twenty-fifth year. Nevertheless, bishops are to know, that not all who have attained to that age must needs be admitted to the aforesaid orders, but those only who are worthy, and whose commendable life is an old age. Regulars likewise shall not be ordained under the above age, nor without a diligent examination by the bishop; all privileges whatsoever in this regard being completely set aside.

Translation: J. Waterworth, The Canons and Decrees of the Council of Trent (1848), Hanover Historical Texts Project transcription (1995).