וּבְנֵ֨י יַעֲקֹ֜ב בָּ֤אוּ מִן־הַשָּׂדֶה֙ כְּשׇׁמְעָ֔ם וַיִּֽתְעַצְּבוּ֙ הָֽאֲנָשִׁ֔ים וַיִּ֥חַר לָהֶ֖ם מְאֹ֑ד כִּֽי־נְבָלָ֞ה עָשָׂ֣ה בְיִשְׂרָאֵ֗ל לִשְׁכַּב֙ אֶת־בַּֽת־יַעֲקֹ֔ב וְכֵ֖ן לֹ֥א יֵעָשֶֽׂה׃
Meanwhile Jacob’s sons, having heard the news, came in from the field. They were distressed and very angry, because he had committed an outrage in Israel by lying with Jacob’s daughter – a thing not to be done.
Genesis 34:7 (Revised JPS, 2023)
In the rabbinical commentary, there’s a discussion about what “a thing not to be done” indicates.
Rashi suggests that even the Gentiles, since the time of the Flood, understood that violating a girl was wrong; every nation at the time had outlawed such activity.
Nachmanides counters: the Canaanites did not consider it immoral, and the text is highlighting only what is forbidden to the Jews.
Either way, the reader is told to agree with the anger of the brothers. It was a thing not to be done.