Exod 3:2

“When the almighty Lord of the universe began to legislate through the Word and decided to make his power visible to Moses, he sent Moses a divine vision with the appearance of light, in the burning bush. Now a bramble bush is full of thorns. So too when the Word was concluding his legislation and his stay among men as their Lord, again he permitted himself to be crowned with thorns as a mystic symbol. Returning to the place from which he had descended, the Word renewed that by which he had first come, appearing first in the bush of thorns and later being surrounded with thorns that he might show that all was the work of the same one power. He is one, and his Father is one, the eternal beginning and end.”

“And when an angel appears to Moses, Holy Scripture also makes it plain, saying, "The angel of the Lord appeared to him in a flame of fire in a bush." But when it refers to the actual being who replies, it calls him God and Lord and no longer an angel. It is equally clear in its distinction between the angel and the Lord in the account of what happened at the Red Sea.”

“The vision and the voice are in the one place, nor is anyone else heard except the one who is seen. He who is an angel of God when he is seen is the same one who is the Lord when he is heard, but he himself who is the Lord when he is heard is recognized as the God of Abraham, Isaac and Jacob. When he is called the angel of God, it is revealed that this is not his true nature and that he is not alone, for he is the angel of God. When he is called the Lord and God, he is proclaimed as possessing the glory and name of his own nature. Accordingly you have in an angel who appeared in the bush him who is also the Lord and God.”

“What does this mean? The vision that is said to have appeared to Moses in the desert is sometimes called an angel, sometimes the Lord. It means this: he is called angel when he served by speaking externally, and Lord, because he ruled within and produced the conditions needed for speaking. For when the speaker is ruled from within, he is called both angel because of his service and Lord because of his inspiration. Exposition of the Old and New Testament, Exodus”

“It was the Word, breathed from the Father's mouth, Who of the Virgin took a mortal frame. The human form that not yet in the flesh Appeared to Moses wore a brow like ours, Since God, who would by power of the Word Assume a body, made the face the same. Flames rose and seemed to burn the thorny bush. God moved amid the branches set with spines, And tresses of the flames swayed harmlessly, That he might shadow forth his Son's descent Into our thorny members sin infests With teeming briers and fills with bitter woes. For tainted at its root that noxious shrub Had sprouted from its baneful sap a crop Of evil shoots beset with many thorns. The sterile branches suddenly grew bright As God enkindled with his mighty power The leafy boughs, nor harmed the tangled briers. He touched the scarlet berries, blood-red fruits, And grazed the twigs that grew from deadly wood, Shed by the tortured bush with cruel pangs.”

“And here he is first called the angel of the Lord and then God. Is the angel then the God of Abraham, the God of Isaac and the God of Jacob? Therefore he may be rightly understood to be the Savior himself of whom the apostle says, "Whose are the fathers, and from whom is Christ according to the flesh, who is over all things, God blessed forever." Hence even here he, who is the God blessed over all things forever, is not unreasonably understood to be himself the God of Abraham, the God of Isaac and the God of Jacob. But why was he previously called the angel of the Lord when he appeared in the flame of fire from the bush? Was it because he was one of many angels but by a dispensation represented the person of his Lord? Or was something belonging to a creature assumed which might appear visibly for the task at hand and from which words might be uttered in an audible way, whereby the presence of the Lord would also become known to the bodily senses of man, as circumstances required, by means of a creature made subject to him? For if he was one of the angels, who can readily affirm whether the person given him to announce was that of the Son, or of the Holy Spirit, or of God the Father or of the Trinity itself altogether, who is the one and only God, in order that he might say, "I am the God of Abraham, the God of Isaac and the God of Jacob"?For we cannot say that the God of Abraham, the God of Isaac and the God of Jacob is the Son of God and not the Father. Nor will anyone dare to deny that either the Holy Spirit or the Trinity itself, which we believe and understand to be the one God, is the God of Abraham, the God of Isaac and the God of Jacob. For he who is not God is not the God of those fathers. Moreover … not only the Father is God, as all, even the heretics, admit, but the Son also, which willingly or not they are forced to confess, for the apostle says, "who is, over all things, God blessed forever," and the Holy Spirit as well. The same apostle declares, "Therefore glorify God in your body," when he had previously stated, "Do you not know that your bodies are the temple of the Holy Spirit in you, whom you have from God?" And these three are one God, as the sound Catholic faith believes. It is not sufficiently clear which person in the Trinity that angel represented, assuming that he was one of the rest of the angels, and whether it was any person and not that of the Trinity itself.”

“It was not without reason, beloved brethren, nor without the signification of some mystery that there was a flame in the bush: "And the bush was not consumed." Indeed, the bush was a genus of thorns. What the earth has produced for sinful man cannot be put in any kind of praise, for it was first said to man when he sinned: "Thorns and thistles shall the earth bring forth to you." The fact that the bush was not burned, that is, was not seized by the flames, is understood to signify no good. In the flame is recognized the Holy Ghost; in the bush and thorns is represented the hard, haughty Jewish people.”

“A figure preceded in the bush and fire, which Moses saw; a figure in the rod and flower of Aaron; a figure in the fleece and dew of Gideon. Whence Bernard says: "What was shown to Moses in the bush and fire, to Aaron in the rod and flower, to Gideon in the fleece and dew: this Solomon clearly foresaw in the strong woman and her price; more clearly Jeremiah foretold concerning the woman and the man; most clearly Isaiah declared concerning the Virgin and her son; and at last Gabriel made it manifest by greeting the Virgin." Who brought it about that the Virgin conceived? Certainly the Holy Spirit, who is a love fervent, fruitful, undefiled, virile, incorrupt, and deifying. That he is a fervent love is signified to us in the bush and fire.”

“Hence Moses, after he had led the flock across the desert, saw a bush which, though on fire, was not consumed. "I must go over," he said, "to look at this remarkable sight, and see why the bush is not burned." And there he was enlightened. The spiny bush is the flesh liable to suffering; the flame is the soul of Christ full of light and of the fire of love; the light itself is the Godhead; the light joined to the bush by means of the flame is the Godhead joined to flesh by means of the spirit or soul. And so, in order that He be able to quicken the dead and to make sons of God out of mere men, He had to be preeminent.”

“By means of diffusion, as of brightness out of light, of heat out of fire, of a river out of its headspring, of rain out of a full or humid cloud. In the first diffusion, equality is lacking, for brightness is not the same as light. In the second, closeness is lacking, for heat is not close to fire, since it is the principle neither of its form nor of its origin, but is merely an accident. In the third, simultaneity is lacking, for a spring diffuses itself by flowing, and not all at once. In the fourth, fullness is lacking, for not all of the rain is drawn out of a cloud, but only successive drops. Now, join these four conditions to a single diffusion, one of splendor having equality, of heat having closeness and substantiality, of a river or fountain having simultaneity, and of rain having fullness: and in this way, you will have a trace of the eternal generation. Hence, the Son is sometimes compared to brightness: "Being the brightness of His glory," etc.; at other times, to a flame, as in Moses' bush which represented the person of the Son; or again, as a river or spring: "But a spring rose out of the earth. A river rose in Eden." Again, He is sometimes compared to rain: "For just as from the heavens the rain and snow come down and do not return there till they have watered the earth," etc. And, later: "So shall my word be that goes forth from my mouth," that is, from the Father's heart.”