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.
Joannes, the addressee of this letter and letters 64, and 2 (all written in 407) was apparently an enemy of Synesius. The letter is offered here in the translation of A. Fitzgerald.
Letter 63: A Warning
 To Joannes
One should use the friendship of the great, but not abuse it.