Was it fitting for the Old Law to have been given only to the Jewish people?

It seems that the Old Law should not have been given only to the Jewish people:

Objection 1:  As has been explained (a. 2‑3), the Old Law disposed men to the salvation that was to come through Christ.  But that salvation was going to take place among all the nations (in omnibus gentibus) and not just among the Jews—this according to Isaiah 49:6 (“It is a small thing that you should be my servant to raise up the tribes of Jacob and to convert the dregs of Israel.  Behold, I have given you to be the light of the Gentiles, that you may be my salvation even to the farthest part of the earth.”  Therefore, the Old Law should have been given to all the nations and not just to one people.

Objection 2:  As Acts 10:34 says, “God is not a respecter of persons (acceptor personarum), but in every nation, he who fears Him and does works of justice is acceptable to Him.”  Therefore, He should not have opened the way of salvation more to one people than to the others.

Objection 3:  As has been explained (a. 3), the Law was given through angels.  But God has always granted the ministry of the angels to all the nations and not just to the Jews; for Ecclesiasticus 17:14 says, “Over every nation He set a ruler.”  He likewise gave temporal goods to all the nations—and God is less concerned with temporal goods than with spiritual goods.  Therefore, He should likewise have given the Law to all the peoples.

But contrary to this:  Romans 3:1ff. says, “What advantage then does the Jew have?  Much, in every way.  First, because the words of God were committed to them.”  And Psalm 147:20 says, “He has not done thus for any other nation, and He has not made known His judgments to them.”

I respond:  One reason that could be invoked for why the Law was given to the Jewish people rather than to the other peoples is that while the others had fallen into idolatry, the Jewish people alone remained steadfast in the worship of the one God.  And so the other peoples were unworthy to receive the Law, lest what is holy should be given to the dogs.
However, this argument does not seem suitable.  For the Jewish people fell into idolatry even after the Law had been given—which was a more grievous sin, as is clear from Exodus 32 and from Amos 5:25-26 (“Did you offer victims and sacrifices to me in the desert for forty years, O house of Israel?  But you carried a tabernacle for your Moloch and the image of your idols, the star of your god, which you made for yourselves.”)  Again, Deuteronomy 9:6 says explicitly, “Know that it is not because of your acts of justice that the Lord your God gives you this excellent land for your possession; for you are an utterly stiff‑necked people.”
Instead, the correct reason is given in the preceding verse:  “..... in order that the Lord might fulfill His word, which He promised by oath to your fathers, Abraham, Isaac, and Jacob.”  In Galatians 3:16 the Apostle shows which promise had been made to them, saying, “To Abraham were the promises made and to his seed.  He does not say, ‘and to your seeds’, as of many, but ‘and to your seed’, as of one, who is the Christ.”  Therefore, God gave the Law and other special benefits to that people because of the promise He had made to their fathers that the Christ would be born of them.  For it was fitting that the people from whom the Christ would be born should be enriched with a special sanctification—this according to Leviticus 19:2 (“You will be holy, because I am holy.”)
Again, it was not because of the merits of Abraham himself that such a promise was made to him; rather, it was because of his gratuitous election (electio) and calling (vocatio).  Hence, Isaiah 41:2 says, “Who has raised up the just one from the east, has called him to follow Him?”
So, then, it is clear that the patriarchs received the promise solely out of a gratuitous election, and that the people that descended from them received the Law—this according to Deuteronomy 4:36‑37 (“You heard His words out of the midst of the fire, because He loved your fathers, and chose their seed after them”).
However, if one were to ask again why He chose this people in order that the Christ might be born from them, then the response that Augustine gives in Super Ioannem is the right one:  “Why did he choose this one and not that one?  Do not look for an answer, if you do not want to be mistaken.”

Reply to objection 1:  Even though the future salvation through the Christ had been prepared for all the nations, it was still necessary for the Christ to be born from one people, who because of this had prerogatives in preference to the others.  Accordingly, Romans 9:4-5 says, “..... to whom [read:  the Jews] belongs the adoption as of children of God, and the testament and the giving of the law ..... to whom belong the fathers and from whom comes the Christ, according to the flesh.”

Reply to objection 2:  Respect for persons [or favoritism] (acceptio personarum) is possible in the case of things that are given because they are [in some sense] owed, but there is no question of favoritism in the case of things that are conferred gratuitously.  For one is not playing favorites if out of generosity he gives something of his own to one person and not to another.  By contrast, if he were responsible for dispensing communal goods (si esset dispensator bonorum communium) and did not distribute them equitably according to the merits of the relevant persons, then he would be playing favorites.
Now it is out of His graciousness (ex sua gratia) that God confers salvific benefits on the human race.  Hence, there is no favoritism if He confers these benefits on some in preference to others.  This is why Augustine says in De Praedestinatione Sanctorum:  “All those whom God instructs are such that it is by His mercy (misericordia) that He instructs them; and those whom He does not instruct are such that it is by His justice (iudicium) that He does not instruct them.”  For this stems from the condemnation of the human race because of the sin of the first parent.

Reply to objection 3:  The gifts of grace are taken away from man because of sin, but his natural gifts are not taken away.  Among the latter is the ministry of the angels, which is required by (a) the very ordering of natures, so that the lowest beings should be governed by middle‑level beings, as well as by (b) the corporeal gifts that God grants not only to men but also to beasts—this according to Psalm 35:7 (“Men and beasts You will preserve, O Lord”).