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.
The text of Letter 147 (in some editions: 146), in which he congratulates someone who has become a monk, is offered here in the translation by A. Fitzgerald. It is written in 412.
Letter 147 (146): Congratulation to a novice
 To Joannesnote
I think you are a happy man beyond all power of expression, inasmuch as you have left us, poor wretches. "wandering in the darkened meadow of Ate",note tossed about as we are amidst earthly thoughts. While still alive you have raised yourself above these, and have entered into the happy life, unless your friend Ganus - in speaking of you and in conveying your messages to us - thinks it incumbent upon him to utter a bit of falsehood as well, for goodwill has a dreadful way of concealing the truth.
 This very Ganus tells us then that you are living in a monastery, and that if you ever come into town, it is only to consult books, and so much of their contents as pertains to theology. He also says that you were wearing the coarse, dark mantle. The mantle would lose nothing from being white, for what is clear and luminous to the eyes, would be better suited to the pure character. But if you have given your approval to the dark one out of zeal for any who assumed it before you, I give mine to all that is undertaken from a divine motive. For the motive of an action justifies the doer of it, and it is in the intention that virtue resides.
 I congratulate you, therefore, on having achieved offhand the end that we have long been hammering at with great difficulty. Pray with us, that we also may reach it. May we derive some benefit from the thought that we have devoted to philosophy, and may we not have passed our lives over books in vain!