Nicene and Post-Nicene Fathers: Series II/Volume XI/John Cassian/The Twelve Books/Book XII/Chapter 23
Chapter XXIII.
How perfection can only be attained through the virtue of humility.
And so it is clearly shown that none can attain the end of perfection and purity, except through true humility, which he displays in the first instance to the brethren, and shows also to God in his inmost heart, believing that without His protection and aid extended to him at every instant, he cannot possibly obtain the perfection which he desires and to which he hastens so eagerly.