The Cloud of Unknowing, ed. by Evelyn Underhill, [1922], at sacred-texts.com
That by Virtue of this word sin is not only destroyed, but also Virtues begotten.
AND, therefore, if thou wilt stand and not fall, cease never in thine intent: but beat evermore on this cloud of unknowing that is betwixt thee and thy God with a sharp dart of longing love, and loathe for to think on aught under God, and go not thence for anything that befalleth. For this is only by itself that work that destroyeth the ground and the root of sin. Fast thou never so much, wake thou never so long, rise thou never so early, lie thou never so hard, wear thou never so sharp; yea, and if it were lawful to do—as it is not—put thou out thine eyes, cut thou out thy tongue of thy mouth, stop thou thine ears and thy p. 114 nose never so fast, though thou shear away thy members, and do all the pain to thy body that thou mayest or canst think: all this would help thee right nought. Yet will stirring and rising of sin be in thee.
Yea, and what more? Weep thou never so much for sorrow of thy sins, or of the Passion of Christ, or have thou never so much mind of the joys of heaven, what may it do to thee? Surely much good, much help, much profit, and much grace will it get thee. But in comparison of this blind stirring of love, it is but a little that it doth, or may do, without this. This by itself is the best part of Mary without these other. They without it profit but little or nought. It destroyeth not only the ground and the root of sin as it may be here, but thereto it getteth virtues. For an it be truly conceived, all virtues shall truly be, and perfectly conceived, and feelingly comprehended, in it, without any mingling of the intent. And have a man never so many virtues p. 115 without it, all they be mingled with some crooked intent, for the which they be imperfect.
For virtue is nought else but an ordained and a measured affection, plainly directed unto God for Himself. For why? He in Himself is the pure cause of all virtues: insomuch, that if any man be stirred to any one virtue by any other cause mingled with Him, yea, although that He be the chief, yet that virtue is then imperfect. As thus by example may be seen in one virtue or two instead of all the other; and well may these two virtues be meekness and charity. For whoso might get these two clearly, him needeth no more: for why, he hath all. p. 116