Augustine of Hippo

But who shall say that Christ and Christians have no connection with Israel, seeing that Israel was the grandson of Abraham, to whom first, as afterwards to his son Isaac, and then to his grandson Israel himself, that promise was given, which I have already mentioned, namely: “In your seed shall all nations be blessed”? That prediction we see now in its fulfillment in Christ. For it was of this line that the Virgin was born, concerning whom a prophet of the people of Israel and of the God of Israel sang in these terms: “Behold, a virgin shall conceive, and bear a son; and they shall call his name Emmanuel.” For by interpretation, Emmanuel means “God with us.” This God of Israel … has forbidden the worship of other gods, … has forbidden the making of idols, … has commanded their destruction, … has by his prophet predicted that the Gentiles from the ends of the earth would say, “Surely our fathers have worshiped lying idols, in which there is no profit.” This same God is he who, by the name of Christ and by the faith of Christians, has ordered, promised and exhibited the overthrow of all these superstitions.

You must appreciate, brothers and sisters, what a tremendous desire possessed the saints of old to see the Christ. They knew he was going to come, and all those who were living devout and blameless lives would say, “Oh, if only that birth may find me still here! Oh, if only I may see with my own eyes what I believe from God’s Scriptures!” The saints who knew from the holy Scripture that a virgin was going to give birth as you heard when Isaiah was read: “Behold, a virgin shall conceive in the womb and shall bear a son, and his name shall be called Emmanuel.” What Emmanuel means the Gospel declares to us, saying, “which is interpreted, God with us.” So do not let it surprise you, unbelieving soul, whoever you are, do not let it strike you as impossible that a virgin should give birth, and in giving birth remain a virgin. Realize that it was God who was born, and you will not be surprised at a virgin giving birth. So then, to prove to you how the saints and just men and women of old longed to see what was granted to this old man Simeon, our Lord Jesus Christ said, when speaking to his disciples, “Many just men and prophets have wished to see what you see and have not seen it; and to hear what you hear and have not heard it.”

The fact that the one who talked to Moses is called both the angel of the Lord and the Lord raises a big problem, which calls not for hasty assertion but for careful investigation. There are two opinions that can be put forward about it, of which either may be true, since they both fit the faith. When I say that either may be true, I mean whichever of them was intended by the writer. When we are searching the Scriptures, we may of course understand them in a way in which the writer perhaps did not; but what we should never do is understand them in a way which does not square with the rule of faith, with the rule of truth, with the rule of piety. So I am offering you both opinions. There may be yet a third that escapes me. Anyway, of these two propositions, choose whichever you like. Some people say that the reason why he is called both the angel of the Lord and the Lord is that he was in fact Christ, of whom the prophet says plainly that he is “the angel of great counsel.” “Angel” is a word signifying function, not nature. “Angel” is Greek for the Latin nuntius. So “Messenger” is the name of an action: you are called a messenger for doing something, namely, for bringing some message. Now who would deny that Christ brought us a message about the kingdom of heaven? And then an angel, that is to say, a messenger, is sent by the one who wants to give a message by him. And who would deny that Christ was sent? So often did he say, “I did not come to do my own will but the will of him who sent me,” that he of all people is the one who was sent. After all, that pool at Siloam “means Sent.” That is why he told the man whose eyes he anointed with mud to wash his face there. No one’s eyes are opened except those of the person who is cleansed by Christ. So then, the angel and the Lord are one and the same.

David was the king of Israel and the son of Jesse at a certain time in the Old Testament, when the New Testament was still hidden there in the Old, like a fruit in its root. For if you seek the fruit in its root, you will not find it. But neither would you find the fruit in the branch, unless it had first come from the root.At that time, then, the first people had come from the seed of Abraham carnally. The second people, those who belong to the New Testament, also belong to the seed of Abraham, but spiritually. Those first people who were still carnal, therefore, among whom very few prophets understood both what was to be desired from God and when to announce it publicly, foretold this future time and the advent of our Lord Jesus Christ.
Insofar as Christ himself was born according to the flesh, he was hidden in the root, in the seed of the patriarchs, and was to be revealed at a certain time, like fruit appearing on the branch, as it is written: “A rod will bloom from the root of Jesse.” The same is true of the New Testament, which was hidden in Christ throughout those earlier times and was known only to the prophets and to a very small group of godly persons, not as the manifestation of present realities but as a revelation of future events. For what does it mean, brothers, if I can remind you of one specific event, that Abraham, sending his faithful servant to betroth a wife to his only son, makes him swear to him and in the oath says to him, “Put your hand under my thigh and swear”? What was in the thigh of Abraham upon which the man put his hand and swore? What was there, except what was then promised to him: “in your seed, all the peoples will be blessed”? The thigh signifies the flesh. From the flesh of Abraham, through Isaac and Jacob and, without naming everyone, through Mary, came our Lord Jesus Christ.

"The love of God has been poured out in our hearts through the Holy Spirit who has been given to us."That the Holy Spirit is suggested by the number seven anybody knows who can read. But listen anyway, those of you who read carelessly, or perhaps cannot read. This is how God presents the Holy Spirit through the prophet Isaiah: "The Spirit," he says, "of wisdom and understanding, of counsel and fortitude, of knowledge and piety, the Spirit of the fear of God." This is the sevenfold Spirit who is also called down upon the newly baptized. The law is the Decalogue; the Ten Commandments, you see, were written on tablets, but stone ones still, because of the stubborn hardness of the Jews. After the Spirit came, what does the apostle say? "You yourselves are our letter, not written with ink but with the Spirit of the living God; not on tablets of stone, but on the fleshly tablets of the heart." Take away the Spirit, the letter kills, because it finds the sinner guilty, doesn't set him free. That's why the apostle says, "For we are not sufficient of ourselves to think anything as coming from ourselves; but our sufficiency is from God, who has made us sufficient to be ministers of the new covenant, not in the letter, but in the Spirit. For the letter kills, but the Spirit brings to life." So add seven to ten, if you wish to fulfill all justice. When you are commanded by the law to do something, ask the Spirit to help you.