בַּעֲשׂוֹתְךָ֥ נוֹרָא֖וֹת לֹ֣א נְקַוֶּ֑ה יָרַ֕דְתָּ מִפָּנֶ֖יךָ הָרִ֥ים נָזֹֽלּוּ׃
quando hai fatto cose tremende che non cercavamo— Oh che verrai giù, che le montagne possano tremare alla tua presenza!—
Rashi on Isaiah
When You performed against the Egyptians and against all the adversaries awesome deeds, that we did not hope You would perform all those awesome deeds, for we were unworthy of them.
Rashi on Isaiah
You descended to Mount Sinai, then mountains dripped from before You. In this manner, Dunash son of Labrat explained it.