בַּעֲשׂוֹתְךָ֥ נוֹרָא֖וֹת לֹ֣א נְקַוֶּ֑ה יָרַ֕דְתָּ מִפָּנֶ֖יךָ הָרִ֥ים נָזֹֽלּוּ׃
Lorsque tu accomplis de redoutables prodiges, que nous ne pouvions espérer, tu descendis, et les montagnes chancelèrent à ton approche.
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.