The practice of business or trade by clerics and religious was strictly prohibited from the first centuries of the Church. Appropriate decisions were made at the Councils of Nicaea, Chalcedon, Lateran (IV) and Trent. In the 1917 Code of Canon Law, the legislator regulated the analysed matter in can. 142 and 2380. They were the source of the work of the Pontifical Commission for the Authentic Interpretation of the Code of Canon Law. According to the legislator’s disposition contained in can. 286 of the 1983 Code of Canon Law “Clerics are prohibited from conducting business or trade personally or through others, for their own advantage or that of others, except with the permission of the legitimate ecclesiastical authority.” The breach of the above prohibition was punishable by a mandatory indeterminate ferendae sententiae penalty, which should be imposed on the cleric or religious, depending on the gravity of the delict.