Nicene and Post-Nicene Fathers, Ser. II, Vol. XI:
The Works of John Cassian.: Chapter XIII. The teaching of the elders on the method of acquiring purity.

Chapter XIII.

The teaching of the elders on the method of acquiring purity.

Wherefore it is now time to produce, in the very words in which they hand it down, the opinion of the Fathers; viz., of those who have not painted the way of perfection and its character in high-sounding words, but rather, possessing it in deed and truth, and in the virtue of their spirit, have passed it on by their own experience and sure example. And so they say that no one can be altogether cleansed from carnal sins, unless he has realized that all his labours and efforts are insufficient for so great and perfect an end; and unless, taught, not by the system handed down to him, but by his feelings and virtues and his own experience, he recognizes that it can only be gained by the mercy and assistance of God. For in order to acquire such splendid and lofty prizes of purity and perfection, however great may be the efforts of fastings and vigils and readings and solitude and retirement applied to it, they will not be sufficient to secure it by the merits of the actual efforts and toil. For a man’s own efforts and human exertions will never make up for the lack of the divine gift, unless it is granted by divine compassion in answer to his prayer.