This is a great note from St Augustine. He gives grace not because they know him but they do not know him. He gives grace so that they may know Him so that they may be made upright.
“This holy meditation preserves “the children of men, who put their trust under the shadow of God’s wings,” so that they are “drunken with the fatness of His house, and drink of the full stream of His pleasure. For with Him is the fountain of life, and in His light shall they see light. For He extendeth His mercy to them that know Him, and His righteousness to the upright in heart.” He does not, indeed, extend His mercy to them because they know Him, but that they may know Him; nor is it because they are upright in heart, but that they may become so, that He extends to them His righteousness, whereby He justifies the ungodly.
This meditation does not elevate with pride: this sin arises when any man has too much confidence in himself, and makes himself the chief end of living. Impelled by this vain feeling, he departs from that fountain of life, from the draughts of which alone is imbibed the holiness which is itself the good life,—and from that unchanging light, by sharing in which the reasonable soul is in a certain sense inflamed, and becomes itself a created and reflected luminary; even as “John was a burning and a shining light,” who notwithstanding acknowledged the source of his own illumination in the words, “Of His fulness have all we received.”
Whose, I would ask, but His, of course, in comparison with whom John indeed was no light at all? For “that was the true light, which lighteth every man that cometh into the world.” Therefore, in the same psalm, after saying, “Extend Thy mercy to them that know Thee, and Thy righteousness to the upright in heart,” he adds, “Let not the foot of pride come against me, and let not the hands of sinners move me. There have fallen all the workers of iniquity: they are cast out, and are not able to stand.”
Since by that impiety which leads each to attribute to himself the excellence which is God’s, he is cast out into his own native darkness, in which consist the works of iniquity. For it is manifestly these works which he does, and for the achievement of such alone is he naturally fit. The works of righteousness he never does, except as he receives ability from that fountain and that light, where the life is that wants for nothing, and where is “no variableness, nor the shadow of turning.””
From Augustine’s “The Spirit and the Letter” 11.7