In several places, the New Testament speaks of the Torah as being, ‘given by angels.’
The first reference is spoken of by Stephen in the book of Acts:
“Who have received the Law by the disposition of angels, and have not kept it”
Acts 7:53
Later, we find another mention by Paul:
“Wherefore then serves the Law? It was added because of transgressions, till the seed should come to whom the promise was made; and it was ordained by angels in the hand of a mediator.”
Galatians 3:19
A third reference is located in the book of Hebrews:
“The word spoken by angels was steadfast, and every transgression and disobedience received a just recompense of reward.”
Hebrews 2;2
Accusations are made that this is an example of multiple New Testament texts teaching something foreign to Judaism, as the Torah itself shows that G-d gave the Torah to Moshe to give to Israel and nowhere in the rest of the Tanakh does it say otherwise.
Thus we are faced with the question: Is this found in Jewish tradition or an invention? This is the ‘right’ question to ask, as there are other topics discussed in oral Torah that are nowhere found in the words of the Tanakh. For instance, the entity called “Lilith” is mentioned multiple times in Talmud, Midrash Rabbah, the Zohar and many other texts, yet not in the Tanakh. One can also argue that the very subject of ‘the messiah’ is not found anywhere in the literal text of Tanakh and is a product of aggadah, the non-binding portion of the oral Torah.
An outside source referencing this concept, close to that time period, is Josephus, who mirrors the claims of the New Testament.
“And for ourselves, we have learned from G-d the most excellent of our doctrines, and the most holy part of our law, by angels or ambassadors.”
Antiquities of the Jews 15:163
This was written around 93CE. We have no reason to believe Josephus would ‘parrot’ a non-Jewish concept found in the writings of the New Testament, if he even had access to them.
A more significant reference are the scrolls of the “Book of Jubilees” found at Qumran. Scholars date this no later than 100BCE, so it would be a certain reflection of the views within Judaism at the time of the New Testament.
In this text we find specific references to the idea of angels serving as a type of intermediary between G-d and Moses at Sinai:
“And He said to the angel of the presence: “Write for Moses from the beginning of creation till My sanctuary has been built among them for all eternity. And the Lord will appear to the eyes of all, and all will know that I am the God of Israel and the Father of all the children of Jacob, and King on Mount Zion for all eternity. And Zion and Jerusalem will be holy.” And the angel of the presence who went before the camp of Israel took the tables of the divisions of the years –from the time of the creation–of the law and of the testimony of the weeks, of the jubilees, according to the individual years, according to all the number of the jubilees [according to the individual years], from the day of the [new] creation †when† the heavens and the earth shall be renewed and all their creation according to the powers of the heaven, and according to all the creation of the earth, until the sanctuary of the Lord shall be made in Jerusalem on Mount Zion, and all the luminaries be renewed for healing and for peace and for blessing for all the elect of Israel, and that thus it may be from that day and unto all the days of the earth. And the angel of the presence spake to Moses according to the word of the Lord, saying: Write the complete history of the creation, how in six days the Lord God finished all His works and all that He created, and kept Sabbath on the seventh day and hallowed it for all ages, and appointed it as a sign for all His works.”
Jubilees 1:27-2:1
This idea of angels being ‘involved’ in a process where the Torah speaks of ‘G-d,’ is reflected in another established Jewish text:
“And G-d said to the ministering Angels who had been created on the second day of the Creation of the worlds: ‘Let us make Man.’ When Moses wrote the Torah and came to this verse, ‘Let us make Man;’ which is in the plural and implies that there is more than one Creator, he asked: ‘Sovereign of the Universe! Why do you thus furnish a pretext for heretics to maintain that there is a plurality of divinities?’ And G-d replied: ‘Write! Whoever wishes to be foolish in error will be foolish in error! Instead, let them learn from their Creator who created all that exists!‘ Yet when He came to create Man He took council with the ministering Angels.”
Targum Yonatan; Midrash Bereshith
Further, the Rambam says the following regarding angels and each act of G-d:
“In other passages our Sages expressed it more decidedly: “God does nothing without consulting the host above” (the word familia, used in the original, is a Greek noun, and signifies “host”). On the words, “what they have already made” (Ecclessiastes ii. 12), the following remark is made in Bereshit Rabba and in Midrash Koheleth: “It is not said ‘what He has made,’ but ‘what they have made’; hence we infer that He, as it were, with His court, have agreed upon the form of each of the limbs of man before placing it in its position, as it is said, ‘He hath made thee and established thee'” (Deuteronomy 32:6). In Genesis Rabba 51:2) it is also stated, that wherever the term “and the Lord” occurred in Scripture, the Lord with His court is to be understood. … There is only this difference in the names employed — he (Aristotle) uses the term “Intelligences,” and we say instead “angels.” His theory is that the Intelligences are intermediate beings between the Prime Cause and existing things, and that they effect the motion of the spheres, on which motion the existence of all things depends. This is also the view we meet with in all parts of Scripture; every act of God is described as being performed by angels. But “angel” means “messenger”; hence every one that is entrusted with a certain mission is an angel. Even the movements of the brute creation are sometimes due to the action of an angel, when such movements serve the purpose of the Creator, who endowed it with the power of performing that movement; e.g., “God hath sent His angel, and hath shut the lions’ mouths that they have not hurt me. (Daniel 6:22)”
Guide for the Perplexed, part 2, chapter 6
Even where we are told ‘G-d Himself’ is involved, we still find an angel (the ‘destroyer’) involved:
“The Lord will pass to smite the Egyptians, and He will see the blood on the lintel and on the two doorposts, and the Lord will pass over the entrance, and He will not permit the destroyer to enter your houses to smite you.”
Exodus 12:23
There is also this reference, from Midrash, on the Biblical book Song of Songs:
Another matter, “let him kiss me with the kisses of his mouth,” Rabbi Yoḥanan said: An angel would take the utterance from before the Holy One blessed be He, each and every utterance, and circulate them before each and every Israelite and say to him: ‘Do you accept this utterance upon yourself? There are such and such laws in it, there are such and such punishments in it, there are such and such decrees in it, and so many commandments, and so many a fortiori inferences, there are such and such rewards in it.’ The Israelite would say to him: ‘Yes.’ [The angel] would then say to him: ‘Do you accept the divinity of the Holy One blessed be He?’ And he would say to him: ‘Yes, yes.’ Immediately he would kiss him on his mouth; that is what is written: “You have been shown in order to know [that the Lord, He is God]” (Deuteronomy 4:35), by means of an agent.
Song of Songs Rabbah 1:2
Taking all of this Jewish tradition into account, especially texts from the time of the NT that are specific to Sinai, it is well within the bounds of sound academic standards to accept the words of the New Testament on this issues as not being foreign to “Jewish thought” on the matter.