Philoxenus of Mabbug

And the blessed David said that the upright and men of integrity clave unto him, and it is well known that integrity is born of simplicity. Now my speech here referreth to the purity of spirit which ariseth in the soul after the flight of all wickedness; for the order of natural simplicity is one thing, and the order of purity of the spirit is another. The simplicity of nature is the beginning of the path of the doctrine of Christ, but purity of spirit is the end of the path of righteousness. And whosoever beginneth in simplicity endeth in purity, even also as the blessed Apostles, when they were chosen, at the beginning were simple men; but at the end of the dispensation after they had received the Holy Ghost, they were shewn to be pure men. Now purity is this: a man should by toil, and weariness, and striving against all hateful motions separate from him the filth of wickedness, and cast it away from him, and the purity and undefiledness of pure thoughts and of the thoughts which are moved by the Spirit, and are above all doubt, should abide in him. And simplicity is that which is not stirred up naturally in these thoughts; and that which simplicity distinguisheth not when it entereth, it must overcome in contest, and in wisdom must reject, and expel, and cast forth from the place of its purity.