The Epistle of Barnabas
Barnabae epistula
Barnabas. The Apostolic Fathers with an English Translation In Two Volumes. Vol. I. Lake, Kirsopp, translator. Cambridge, MA: Harvard University Press; London: William Heinemann Ltd. 1912.
I have therefore reckoned that, if I make it my care in your behalf to communicate somewhat of that which I received, it shall bring me the reward of having ministered to such spirits, and I hasten to send you a short letter in order that
your knowledge may be perfected along with your faith.