Do not, even for the sake of defending the faith, converse with heretics, for fear less their words instill their venom into thy mind. If thou meet with a book said to be by one of the heretics, read it not, lest it fill thy heart with deadly poison; but so continue in that doctrine which thou hast learnt in holy church, as neither to add or to take from it.
Isaias, Abbot [4th Cent.]
Further reading
This saying attributed to Abbot Isaias reflects the severe counsel found in early ascetic writing. The Sayings of the Desert Fathers, translated by Benedicta Ward, offers a wider introduction to the voices, disciplines, and spiritual concerns of that monastic world.