Abbot Isaac on the Nature of Prayer

The aim of every monk, and the perfection of his heart, is directed toward continual and unbroken perseverance in prayer. As far as human frailty allows, it strives to gain an unshakable calm of mind and a lasting purity. For the sake of this we seek, tirelessly and constantly, to practice all bodily labors and to keep a crushed spirit. And between these two there is a kind of mutual and inseparable union. For just as the crown of the whole building of the virtues is the perfection of prayer, so unless everything has been joined and bound together by this as its crown, it cannot possibly stay strong and stable. The lasting and continual calm in prayer we are speaking of cannot be secured or brought to completion without the virtues; and in the same way the virtues that lay its foundations cannot be fully gained without persistence in prayer. [a]

And so we will not be able either to treat properly of the effect of prayer, or in a quick discourse to reach its main end, which is gained by laboring at all the virtues, unless we first list and discuss one by one all the things that must be either rejected or secured for its sake. As the parable in the Gospel teaches, whatever concerns the building of that spiritual and most lofty tower must be reckoned up and carefully considered beforehand. But even when these things are prepared, they will be of no use, nor will they allow the lofty height of perfection to be properly set on them, unless first all faults are cleared away, the decayed and dead rubbish of the passions is dug out, and the strong foundations of simplicity and humility are laid on the solid and, so to speak, living soil of our heart, or rather on that rock of the Gospel. Built in this way, this tower of spiritual virtues will rise and be able to stand unmoved, and be raised to the utmost heights of heaven, fully assured of its stability. For if it rests on such foundations, then though heavy storms of passions break over it, though mighty torrents of persecutions beat against it like a battering ram, though a furious tempest of spiritual enemies dashes against it and attacks it, not only will no ruin overtake it, but the onslaught will not harm it even in the slightest degree.