From On the Prayer of Jesus: The Classic Guide to the Practice of Unceasing Prayer as Found in The Way of the Pilgrim
Among the mysterious, wonderful properties of the name of Jesus is the power and property of expelling demons. This property was disclosed by the Lord himself. He said that those who believe in him, in his name they will cast out demons. (Mark 16:17) Special attention must be paid to this property of the name of Jesus, because it is of the greatest importance for those practicing the Prayer of Jesus. First of all a few words must be said concerning the dwelling of demons in human beings. This occurs in two ways: one can be called sensible, the other moral. Satan dwells sensibly in a man when with his being he occupies the man’s body, and tortures body and soul. In this way it is possible for one devil to live in a man, and it is also possible for many devils to live in the same man. Then a man is called possessed or a demoniac. From the Gospel we see that our Lord healed people possessed with devils. The Lord’s disciples also healed them; they expelled demons from people by the name of the Lord.
Satan dwells morally in a man when the man becomes a doer of the devil’s will. It was in this way that Satan entered into Judas Iscariot, (John 13:27), that is, he controlled his reason and will, and became one with him in spirit. All nonbelievers in Christ were and are in this state, as the holy apostle Paul says to Christians who had been converted to Christianity from paganism: And you he made alive, when you were dead through your trespasses and sins in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience. Among these we all once lived in the passions of our flesh, following the desires of the flesh and the mind, and so we were by nature children of wrath, like the rest of mankind. (Ephesians 2:1-3) In this state more or less, according to the degree of their sinfulness, are those who have been baptized into Christ but who have become estranged from him by sin. That is how the holy Fathers understand Christ’s words regarding the return of the devil with seven other more evil spirits to the temple of the soul from which it had been expelled by the Holy Spirit. (Matthew 12:43-45) When spirits enter in this way, they can be driven out again by the Prayer of Jesus, accompanied by a life of constant and diligent penitence.
Let us take up this neglected work so directly concerned with our salvation! Let us do all in our power to expel demons that have entered us through our negligence by the Prayer of Jesus. It has the property of reviving those deadened by sin, and it has the property of driving out devils. I am the resurrection and the life, said the Savior. He who believes in me, even though he dies, will live. (John 11:25) These signs will accompany those who believe: in my name they will cast out demons. (Mark 16:17) The Prayer of Jesus both reveals the presence of demons in a man, and drives them out of the man. Herein is accomplished something like what took place when the Lord expelled the demon from the possessed boy after his transfiguration. When the lad saw the Lord coming, the spirit convulsed the boy and he fell on the ground and rolled about, foaming at the mouth. (Mark 9:20) When the Lord commanded the evil spirit to leave its victim, out of malice and wickedness as it came out it shrieked out and violently convulsed the boy so that it seemed as if he were dead.
The power of Satan, which dwells in a man as a result of his dissolute life unnoticed and unrealized, when it hears the name of the Lord Jesus invoked in prayer, becomes agitated and confused. It stirs up all the passions and by this means reduced the whole man to a terrible state of agitation and produces in the body various strange maladies. It was in this connection that Saint John the Prophet said: “It only remains for us weak creatures to have recourse to the name of Jesus, for the passions are demons and depart at the invocation of this name.” That means that the action of the passions and demons is a combined action; the demons act by means of the passions. When we see a special disturbance and excitement of the passions accompanying the Prayer of Jesus, let us not be dejected or perplexed by it. On the contrary, let us take courage and prepare ourselves for the struggle and for the most diligent prayer in the name of Jesus as having received a clear sign that the Prayer of Jesus has begun to produce its proper effect in us.
Saint John Chrysostom says:
The remembrance of the name of Jesus rouses the enemy to battle. For a soul that forces itself to pray the Prayer of Jesus can find anything by this prayer, both good and evil. First it can see evil in the recesses of its own heart, and afterwards good. This prayer can stir the snake to action, and this prayer can lay it low. This prayer can expose the sin that is living in us, and this prayer can eradicate it. This prayer can stir up in the heart all the power of the enemy, and this prayer can conquer it can gradually root it out. The name of the Lord Jesus Christ, as it descends into the depths of the heart, will subdue the snake which controls its ranges, and will save and quicken the soul. Continue constantly in the name of the Lord Jesus that the heart may swallow the Lord and the Lord the heart, and that these two may be one. However, this is not accomplished in a single day, nor in two days, but requires many years and much time. Much time and labor are needed in order to expel the enemy and instate Christ.