Sanhedrin 22A

״וכתב הנשתון כתוב ארמית ומתרגם ארמית״. וכתיב: ״לא כהלין כתבא למקרא ופשרה להודעה למלכא״. [מלמד שבאותו היום ניתן] וכתיב: ״וכתב את משנה התורה הזאת״⁠ – כתב הראוי להשתנות.

“And the writing of the letter [hannishtevan] was written in the Aramaic script, and set forth in the Aramaic tongue” (Ezra 4:7). The term “hannishtevan” is similar to the word nishtana, meaning changed, alluding to the fact that the script had been changed. And it is written with regard to the writing on the wall of Belshazzar’s palace: “Then came in all the king’s wise men. But they could not read the writing, nor make known to the king the interpretation” (Daniel 5:8), and the reason they could not read it is that it was written in the new script that Ezra would transmit. And it is written: “That he should write for himself a second [mishne] Torah” (Deuteronomy 17:18), where “second [mishne]” teaches that it is written in a script that is apt to be changed [lehishtannot].

למה נקרא שמו אשורי? שעלה עמהם מאשור.

The baraita continues: Why is this script called Ashurit? Because it ascended with the Jewish people from Ashur when they returned from their exile in Babylonia.

תניא, רבי אומר: בתחלה בכתב זה ניתנה תורה לישראל. כיון שחטאו, נהפך להן לרועץ. כיון שחזרו בהן, החזירו להם, שנאמר: ״שובו לבצרון אסירי התקוה גם היום מגיד משנה אשיב לך״.

It is taught in a baraita (Tosefta 4:5): R' Yehuda HaNasi says: Initially, the Torah was given to the Jewish people in this script, Ashurit, which is in use today. Once the Jewish people sinned, it turned into an impairment for them and they began writing with a different script, Libona’a. Once they repented, the first script was returned to them, and they resumed writing with Ashurit script, as it is stated: “Return to the stronghold, you prisoners of hope; even today do I declare that I will render double [mishne] to you” (Zechariah 9:12), meaning that God restored to the Jewish people this script that had been changed [nishtanna].