Augustine of Hippo : And the surest sign that you have been taught of God is that you put into practice what you have been taught. Of that character are all who are called according to God's purpose, as it is written in the prophets, "They shall be all taught of God." The person, however, who has learned what ought to be done but does not do it, has not yet been "taught of God" according to grace but only according to the law, not according to the Spirit but only according to the letter. There are many who appear to do what the law commands through fear of punishment, not through love of righteousness, and such righteousness as this apostle calls "his own which is after the law"—a thing as it were commanded, not given.… When the free person keeps a commandment, he does it readily. And whosoever learns his duty in this spirit does everything that he has learned ought to be done. — ON ORIGINAL SIN 1:14 Isaac of Nineveh : In the same way He wrote through the prophets, for "He put His laws into their minds and He wrote them on their hearts," so that they should all be "taught of God."If we now set aright our disgraceful lives with the aid of writings on account of the rationality that our nature received from the beginning, how much shall we turn aside from God if we show contempt for the natural book of the heart, the book written by Moses and the prophets, and the light of our Savior's Gospel of life! Hence we shall bring capital punishment upon ourselves if we gain no help from the hidden book, or from the visible one, or from the Gospel of the life-giving commandments of our Lord Jesus Christ. Not even the man who toils and exerts himself in prayer, reading, divine vision, and insight, will make progress in the truth and gain an illumined intellect, unless he aims the intention of his mind toward the strength of what is written by the Spirit on the book of his heart. The veil of the passions that overlays our heart prevents us from truly beholding that which is written on our heart by the Spirit. When we pray, read, and sing praises, we float over the surface of our heart without truly perceiving what lies within. But if we raise the veil of the passions by observing the commandments, then with the eye of the spirit we shall see the truth that is imprinted in our heart. — BOOK OF GRACE 5:74-77 Theodoret of Cyrus : Symmachus translated, "The Lord who takes pity on you says, lowly one, who has not been comforted, I have mercy for you. For I have seen you wandering aimlessly, as if surrounded by the spirits of deceit that have restless thoughts." … He calls godly public behavior a "city." The marks of the saints are various. But all are equally pleasing in God's sight. For that reason he calls them all precious stones, even if they have various characters. By coal is symbolized God's burning love. Sapphire represents the person who hides his virtue, for the hue of sapphire is a deep one. By "jasper" … is designated, I think, the luster of miracle working.… Then Isaiah leaves the figurative way of speaking to put things more clearly: "All your sons shall be taught of the Lord." He has called figuratively "stones," the appearance of virtue. The peace of God is here promised. Paul refers to this construction when he says, "Like a skilled architect I laid the foundation." — COMMENTARY ON Isaiah 17:54.11-14