Of Israel he says, Even unto this day the same veil is upon their heart; " showing that the veil which was on the face of Moses was a figure of the veil which is on the heart of the nation still; because even now Moses is not seen by them in heart, just as he was not then seen by them in eye.
The apostle also says, “Even until this day, whenever Moses is read, a veil lies upon their hearts; but when a man shall turn to the Lord, the veil shall be taken away; and where the Spirit of the Lord is, there is liberty.” For so long as a man does not attend to the spiritual meaning “a veil lies upon his heart,” in consequence of which veil, in other words his duller understanding, the Scripture itself is said or thought to be veiled. This is the explanation of the veil which is said to have covered the face of Moses when he was speaking to the people, that is, when the law is read in public. But if we turn to the Lord, where also the Word of God is and where the Holy Spirit reveals spiritual knowledge, the veil will be taken away, and we shall then with unveiled face behold in the holy Scriptures the glory of the Lord.
Further, if any one ponders over the prophetic sayings with all the attention and reverence they deserve, it is certain that in the very act of reading and diligently studying them his mind and feelings will be touched by a divine breath. He will recognize that the words he is reading are not human utterances but the language of God; and so he will perceive from his own experience that these books have been composed not by human art or mortal eloquence but, if I may so speak, in a style that is divine. The splendor of Christ’s advent has, therefore, by illuminating the law of Moses with the brightness of the truth, withdrawn the veil which had covered the letter of the law and has disclosed, for everyone who believes in him, all those “good things” which lay concealed within.
For since he said that in the reading of the Old Testament the veil remaineth, lest any should think that this that is said is from the obscurity of the Law, he both by other things showed even before what his meaning was, (for by saying, "their minds were hardened," he shows that the fault was their own,) and, in this place too, again. For he said not, 'The veil remaineth on the writing,' but "in the reading;" (now the reading is the act of those that read;) and again, "When Moses is read." He showed this however with greater clearness in the expression which follows next, saying unreservedly, "The veil lieth upon their heart." For even upon the face of Moses it lay, not because of Moses, but because of the grossness and carnal mind of these.
The curtain of the temple is torn, for that which had been veiled in Judea is unveiled to all the nations; the curtain is torn and the mysteries of the law are revealed to the faithful, but to unbelievers they are hidden to this very day. When Moses, the Old Testament, is read aloud by the Jews on every Sabbath, according to the testimony of the apostle: “the veil covers their hearts.” They read the law, true enough, but they do not understand because their eyes have grown so dim that they cannot see. They are, indeed, like those of whom Scripture says: “They have eyes but see not; they have ears but hear not.”
Yet the shadows bring forth the truth, even if they are not at all the truth themselves. Because of this, the divinely inspired Moses placed a veil upon his face and spoke thus to the children of Israel, all but shouting by this act that a person might behold the beauty of the utterances made through him, not in outwardly appearing figures but in meditations hidden within us. Come, therefore, by taking off the veil of the law and by setting the face of Moses free of its coverings, let us behold the naked truth.
But we all with open face beholding as in a glass the glory of the Lord, are changed into the same image, from glory to glory, even as by the Spirit of the Lord."
[AD 220] Tertullian on 2 Corinthians 3:15