In this very short and straightforward decretal (the first of two pieces ascribed to Pontian) our forgers show us the pope writing to one Felix Scribo, who has been defending various priests "against the perfidies of evil men" (contra pravorum hominum insidias). The pope, of course, is convinced that this good conduct is highly pleasing to God.
Most of this letter consists of reassuring pastoral passages lifted from the register of Gregory the Great. Pseudo-Isidore trots out his pet themes only in one brief passage about halfway through: Not only are priests to be honored, but they are not to be accused by pestilential men. And if they're in error, they cannot be corrected by the laity, but only by their felow priests and the pope.
Recipient: Felix Scribo: a fictitious person, though the by-name seems to have been borrowed from one of Gregory the Great's correspondents.
Date: 23 Jan.; the consuls are Severus and Quintianus, from the Liber Pontificalis again
Sources: Gregory the Great, letters; the Bible; a letter of Jerome (?); Benedictus Levita
Contemporary Carolingian Legislation: 816 Council of Aachen (?) -- It's hard to tell whether one particular passage is citing the Jerome epistle or these conciliar acta