By Saint John Cassian the Roman
We pray to You, O Lord Jesus, to whom we have ever prayed, that You would give us words by opening our mouth to "the pulling down of strongholds, destroying arguments and every pretension that exalts itself against the knowledge of God, and bringing into captivity every understanding unto Your obedience":(1) for he is indeed free, who has begun to be led captive by You. Do Thou then be present to this work of yours, and to those of Yours who are striving for You above the measure of their strength. Grant us to bruise the gaping mouths of this new serpent, and its neck that swells with deadly poison, O You who makes the feet of believers to tread unharmed on serpents and scorpions, and to go upon the asp and basilisk, to tread under foot the lion and the dragon. And grant that through the fearless boldness of steadfast innocence, the sucking child may play upon the hole of the asp, and the weaned child thrust his hand into the den of the basilisk.(2) Grant then to us also that we may thrust our hands unharmed into the den of this monstrous and most wicked basilisk; and if it has in any holes, i.e., in the human heart, a lurking or resting place, or has laid its eggs there, or left a trace of its slimy course, do Thou remove from them all the foul and deadly pollution of this most noxious serpent. Take away the uncleanness their blasphemy has brought on them, and purify with the fan of Your sacred cleansing(3) the souls that are plunged in stinking mud, so that the "dens of thieves" may become "houses of prayer":(4) and that in those which are now, as is written, the dwellings where hedgehogs and monsters, and satyrs, and all kinds of strange creatures dwell, there the gifts of Your Holy Spirit, namely the beauty of faith and holiness may shine forth. And as once You destroyed idolatry and cast out images, so make shrines of virtue out of the temples of devils, and let into the dens of serpents and scorpions the rays of shining light, and make out of the dens of error and shame the homes of beauty and splendor. So do Thou pour upon all whose eyes the darkness of heretical obstinacy has blinded, the light of Your compassion and truth, that they may at length with clear and unveiled sight behold the great and life-giving mystery of Your Incarnation, and so come to know You to have been born as true man of that sacred womb of a pure Virgin, and yet to acknowledge that You were always true God.(5)
2. Isaiah 11:8
3. Malachi 3:2-3
4. Matthew 21:13
5. This prayer was written for those heretics who denied the Orthodox doctrine of Christ's Incarnation, so if praying about another heresy it can be inserted towards the end of the last line.
From On the Incarnation, Bk. 7, Ch. 1.