Megillah 3A

בנס היו עומדין!

stood by way of a miracle?

אין, מהוה הוו, ולא הוו ידעי הי באמצע תיבה והי בסוף תיבה, ואתו צופים ותקינו פתוחין באמצע תיבה וסתומין בסוף תיבה.

The Talmud answers: Yes, two forms of these letters did exist at that time, but the people did not know which one of them was to be used in the middle of the word and which at the end of the word, and the Seers came and established that the open forms are to used be in the middle of the word and the closed forms at the end of the word.

סוף סוף ״אלה המצות״, שאין נביא עתיד לחדש דבר מעתה! אלא שכחום וחזרו ויסדום.

The Talmud asks: Ultimately, however, doesn’t the phrase “these are the commandments” (Leviticus 27:34) indicate that a prophet is not permitted to initiate any matter of halakha from now on? Rather, it may be suggested that the final letters already existed at the time of the giving of the Torah, but over the course of time the people forgot them, and the prophets then came and reestablished them.

ואמר רבי ירמיה ואיתימא רבי חייא בר אבא: תרגום של תורה ⁠— אונקלוס הגר אמרו מפי רבי אליעזר ורבי יהושע. תרגום של נביאים ⁠— יונתן בן עוזיאל אמרו מפי חגי זכריה ומלאכי, ונזדעזעה ארץ ישראל ארבע מאות פרסה על ארבע מאות פרסה. יצתה בת קול ואמרה: מי הוא זה שגילה סתריי לבני אדם?

§ The Talmud cites another ruling of R' Yirmeya or R' Ḥiyya bar Abba. R' Yirmeya said, and some say that it was R' Ḥiyya bar Abba who said: The Aramaic translation of the Torah used in the synagogues was composed by Onkelos the convert based on the teachings of R' Eliezer and R' Yehoshua. The Aramaic translation of the Prophets was composed by Yonatan ben Uzziel based on a tradition going back to the last prophets, Haggai, Zechariah, and Malachi. The Talmud relates that when Yonatan ben Uzziel wrote his translation, Eretz Yisrael quaked over an area of 400 parasangs [parsa] by 400 parasangs, and a bat kol emerged and said: Who is this who has revealed My secrets to mankind?