יִתֵּ֧ן יְהוָ֛ה אֶת־מְטַ֥ר אַרְצְךָ֖ אָבָ֣ק וְעָפָ֑ר מִן־הַשָּׁמַ֙יִם֙ יֵרֵ֣ד עָלֶ֔יךָ עַ֖ד הִשָּׁמְדָֽךְ׃
여호와께서 비 대신에 티끌과 모래를 네 땅에 내리시리니 그것들이 하늘에서 네 위에 내려서 필경 너를 멸하리라
Ramban
AND IT SHALL BECOME SMALL DUST OVER ALL THE LAND OF EGYPT. According to the opinion of our Rabbis,204Shemoth Rabbah 11:6. [the small quantity of] soot [in the hands of Moses] became the dust which settled over the whole land of Egypt, and that dust, coming upon man and upon beast, caused them to break forth with boils and blains throughout all the land of Egypt, since it was a burning hot dust. Perhaps the wind caused the dust to enter the homes as well, and there was thus no escape from it. This is a correct [conjecture]. Many times during a drought, the fall of the dew is accompanied by a sort of dust, and it is furthermore written, The Eternal will make the rain of thy land powder and dust.205Deuteronomy 28:24.
It is also possible to say, in line with the plain meaning of Scripture, that the purport of the expression, And it shall become small dust, is that the dust which will be produced in that place from the soot will bring the boils over all the land of Egypt, as He infected the air to do so, it being a decree of the Supreme One.206According to this interpretation, the miracle entailed was thus greater than the one in consonance with the first interpretation, which had the dust throughout the land of Egypt causing the boils and the blains. According to the second interpretation, the soot of the furnace became dust only over the place where the miracle was wrought, which in turn caused the whole atmosphere over Egypt to effect the boils.
It is also possible to say, in line with the plain meaning of Scripture, that the purport of the expression, And it shall become small dust, is that the dust which will be produced in that place from the soot will bring the boils over all the land of Egypt, as He infected the air to do so, it being a decree of the Supreme One.206According to this interpretation, the miracle entailed was thus greater than the one in consonance with the first interpretation, which had the dust throughout the land of Egypt causing the boils and the blains. According to the second interpretation, the soot of the furnace became dust only over the place where the miracle was wrought, which in turn caused the whole atmosphere over Egypt to effect the boils.