וַיֹּ֣אמֶר יְהוָה֮ אֶל־מֹשֶׁה֒ אֱמֹר֙ אֶֽל־אַהֲרֹ֔ן נְטֵ֣ה אֶֽת־מַטְּךָ֔ וְהַ֖ךְ אֶת־עֲפַ֣ר הָאָ֑רֶץ וְהָיָ֥ה לְכִנִּ֖ם בְּכָל־אֶ֥רֶץ מִצְרָֽיִם׃
I rzekł Wiekuisty do Mojżesza: "Powiedz Ahronowi: wyciągnij laskę twoję, a uderz o proch ziemi, i zamieni się w komary po całej ziemi Micraim."
Rashi
אמר אל אהרן SAY UNTO AARON — The dust did not deserve to be smitten by Moses because it had protected him when he slew the Egyptian, for “he hid him in the sand”; and it was therefore smitten by Aaron (Tanchuma; Exodus Rabbah 10:7).
Chizkuni
והיו לכנים, “they will become vermin.” These are the kind of vermin that are products of the dust, but only rarely attack human beings. They emanated from their customary habitat, like the frogs and other plagues.