Prayer is undoubtably the most frequently discussed and most thoroughly developed theme in Saint Isaac….

‘Prayer’, according to Evagrius Pontlcus, ‘is the converse of the mind with God’.1 For Isaac the Syrian, the converse of the mind with God is the highest and most important spiritual activity of a Christian, and cannot be compared with any other endeavor: ‘Just as nothing resembles God, so there is no ministry or work which resembles converse with God in stillness.2 By prayer Isaac understands the whole range of activities which accompany the converse of the mind with God:
Every good care of the intellect directed toward God and every meditation upon spiritual things is delimited by prayer, is called by the name of prayer and under its name is comprehended; whether you speak of various readings, or the cries of a mouth glorifying God, or sorrowing reflection on the Lord, or making bows with the body, or the alleluias of psalmody, or all the other things from which the teaching of genuine prayer ensues.3

According to the understanding traditional in Eastern Christian asceticism, prayer is the basis of a Christian’s spiritual life, a source and cause of all good things. Isaac defines prayer as:
… the refuge of help, a source of salvation, a treasury of assurance, a haven that rescues from the tempest, a light to those who are in darkness, a staff of the infirm, a shelter in time of temptations, a medicine at the height of sickness, a shield of deliverance in war, an arrow sharpened against the face of the enemies, to speak simply: the entire multitude of these good things is found to have its entrance through prayer.4
In another place, he defines prayer as ‘the mind’s freedom and rest from everything of this world and a heart that has completely turned its gaze toward the fervent desire belonging to the hope of future things’.5
At the time of prayer, when a person’s mind is collected and all the senses are brought into harmony, an encounter between God and the person praying takes place. This explains why all spiritual gifts and all mystical visions have been given to the saints at the time of prayer. It was during prayer that an angel appeared to Zacharias and announced the conception of John the Baptist;6 it was during the prayer of the sixth hour that Peter beheld the divine vision;7 it was while Cornelius the Centurion prayed that an angel appeared to him.8
When the High Priest once a year, during the dread time of prayer, entered the Holy of Holies and cast himself down upon his face, . . . he heard the oracles of God through an awesome and ineffable revelation. O how awesome was the mystery which was ministered in this ceremony! So also at the time of prayer were all visions and revelations made manifest to the saints. For what other time is so holy, and by its sanctity so apt for the reception of gifts, as the time of prayer, wherein a man converses with God? At this time, when we make our petitions and our supplications to God, and we speak with him, a human being forcefully gathers together all the movements and deliberations of his soul and converses with God alone, and his heart is abundantly filled with God.9
What are the main requirements which Isaac lays down for true prayer?
First, one should pray with attention and without distraction: external activity should not draw one’s attention from prayer. Isaac cites as an example an ascetic who said: ‘I was amazed when I heard of monks who do handwork in their cells and are able to perform their rule of prayer without omissions and remain free of turbulence. . . . I tell you in very truth, that if I go out to pass water, I am shaken from my habit of mind and its order and I am impeded from the accomplishment of my deeds of excellence’.10
Secondly, one should pray with humility. The prayer of a humble person goes directly from his mouth to God’s ear.11
When you fall down before God in prayer, become in your thought like an ant, like a creeping thing of the earth, like a leech, and like a tiny lisping child. Do not say anything before him with knowledge, but with a child’s manner of thought, draw near God and walk before him, that you may be counted worthy of that paternal providence that fathers have for their small children.12

Thirdly, one should pray with deep affection and tears. The sense of the heart’s affliction, accompanied by bodily labor that is prostrations-should become an integral part of prayer: ‘Reckon every prayer wherein the body does not toil and the heart is not afflicted to be a miscarriage, for this prayer has no soul’.13 At the same time, as Isaac quotes Evagrius, ‘prayer is joy that sends up thanksgiving’.14 The paradoxical combination of affliction of the heart and the spiritual joy of thanksgiving becomes a source of tears, which accompany prayer, especially at its highest stages. ‘The fullness of prayer is the gift of tears’, Isaac says.15
Tears during prayer is a sign that the soul has been deemed worthy of God’s mercy in her repentance, and that her repentance has been accepted, and through her tears the soul has begun to enter into the plain of limpid purity. 16
Fourthly, one should pray with a patience and an ardor that are connected with the love of God:
Love is a fruit of prayer that, by prayer’s contemplation, draws the intellect insatiably toward that for which it longs when the intellect patiently perseveres in prayer without wearying, whether it prays in a visible way, employing the body, or with the mind’s silent reflections, diligently and with ardor. Prayer is the mortification of the will’s motions pertaining to the life of the flesh. For a man who prays correctly is the equal of the man who is dead to the world. And the meaning of ‘to deny oneself’ is this: courageously to persevere in prayer. 17
Fifthly, every word of prayer should come from the depths of the heart. Even if the words of prayer are borrowed from the psalms, they should be uttered as if they were one’s own:
In the verses of your psalmody do not be like a man who borrows words from another, lest … you be left utterly devoid of the compunction and joy to be found in psalmody. Rather, recite the words of psalmody as your very own, that you may utter the words of your supplication with insight and with discriminating compunction.18
Isaac valued psalmody highly and emphasized the necessity of meditating on the words of psalms:
… The wondrous words set out in the Odes which are appointed in the Holy Church, along with all sorts of other lofty words set out by the Spirit in harmonious chants, all these can fulfill the place of perfect prayer in someone: by being meditated upon, they give birth within us to pure prayers and exalted insights, thus bringing us close to luminosity of mind and wonder at God, as well as to all the other things with which the Lord will enlighten you with wisdom in their due time, as you select those verses that are appropriate and offer them up to your Lord with supplication as your intention, repeating them at length and serenely.19
Finally, prayer should be based on faith and absolute trust in God.20 Thus we may not ask God for earthly goods, which God will give us even without our making a special request:
Do not ask of God a thing which he himself, without our asking, has already taken forethought to give … to us. . . . A son does not ask bread of his father, but seeks the great and lofty things of his father’s house. It was on account of the feebleness of the minds of common men that the Lord commanded us to ask for our daily bread ’21 for mark what he commanded to those who are perfect in knowledge and healthy in soul: ‘Take no thought concerning food and raiment…. 22 But seek ye rather the kingdom of God and its righteousness, and all these things will be added unto you’.23
Those who truly believe in God do not ask God ‘Give this to us’, or ‘Take that from us’, and do not take heed of themselves at all, for they perceive in their life the fatherly providence of God. 24 Instead of asking God ‘What will you give me?’, the freeborn soul asks God to preserve the treasury of faith in its heart, ‘though in fact God does not need even this prayer’.25
The main requirements necessary for prayer, according to Isaac, are therefore: attentiveness and the absence of distraction, humility, a deep feeling of contrition accompanied by tears, patience, and ardor, words of prayer uttered out of the depths of the heart, true belief, and trust in God. Such prayer will easily and speedily reach the ears of God.
Sometimes, however, God may appear to be slow in answering prayer and not always to fulfill requests. Isaac gives two reasons for this. The first is the providence of God, by which God gives to everyone according to his measure and ability to receive:

If you should beseech God for a thing and he is slow to hearken to you speedily, do not grieve, for you are not wiser than God. This happens to you either because you are not worthy to obtain your request, or because the pathways of your heart do not accord with your petitions, but rather the contrary, or because your hidden measure is too immature for the greatness of the thing you are asking for.26
Another reason why God seems not to hear our prayer is our own sins:
Since we say that God is plenteous in mercy, why is it that when amidst temptations we unceasingly knock and pray, we are not heard and he disregards our prayer? This we are clearly taught by the Prophet when he says: ‘The Lord’s hand is not little, that it cannot save; nor is he heavy of hearing, that he cannot hear: but our sins have separated us from him, and our iniquities have turned away his face that he doth not hearken’ .27 Remember God at all times, and he will remember you whenever you fall into evils.28
St. Isaac the Syrian