Synesius, Letter 156
Synesius of Cyrene (c.370-c.413) was a Neo-Platonic philosopher who became bishop of Ptolemais in the Cyrenaica. He left behind a small corpus of texts that offer much information about daily life in Late Antiquity, and about the christianization of the Roman world.
In Letter 155, written in 409, Synesius had asked the lawyer Domitian for help. He appears to have asked a favor in return; which Synesius indeed offers in Letter 156. The text is offered here in the translation by A. Fitzgerald.
Letter 156: An Offer to Help
 To Domitian, the Juristnote[He is also the addressee of Letter 155.]
Whatsoever things are righteous to stand in need of allies, and those who come to their rescue may be accounted fortunate, inasmuch as they are co-operating with the upright. It is you whom I have chosen as the bulwark of these principles, as you will defend them with knowledge and skill.
 It is my desire to do good to all whom I can benefit. Do you yourself give me the opportunity! You will gain knowledge of a friendship that you will not yourself regret, and which no one is likely to ridicule.