וַאדֹנָ֨י יְהוִ֜ה הַצְּבָא֗וֹת הַנּוֹגֵ֤עַ בָּאָ֙רֶץ֙ וַתָּמ֔וֹג וְאָבְל֖וּ כָּל־י֣וֹשְׁבֵי בָ֑הּ וְעָלְתָ֤ה כַיְאֹר֙ כֻּלָּ֔הּ וְשָׁקְעָ֖ה כִּיאֹ֥ר מִצְרָֽיִם
주 만군의 여호와는 땅을 만져 녹게 하사 무릇 거기 거한 자로 애통하게 하시며 그 온 땅으로 하수의 넘침 같이 솟아오르며 애굽 강 같이 낮아지게 하시는 자요
Rashi
Yea, it shall rise up wholly like the rain cloud Heb. כָּאֹר. And in another place (9:5), Scripture says: “And it shall come up wholly like the river (כַיְאֹר),” and Jonathan renders them both identically: And a king shall rise upon it with his camp as numerous as the waters of the river, and cover it completely. To me, it seems difficult to define כָאֹר like כַיְאֹר. It can, however be explained like: (Job 36:32) “On the clouds, the rain (אוֹר) is covered. (Job 37:11)” He scatters his rain cloud (אוֹרוֹ) .” And it shall go up wholly like a rain cloud, pitch darkness.