וַתְּדַבֵּ֨ר מִרְיָ֤ם וְאַהֲרֹן֙ בְּמֹשֶׁ֔ה עַל־אֹד֛וֹת הָאִשָּׁ֥ה הַכֻּשִׁ֖ית אֲשֶׁ֣ר לָקָ֑ח כִּֽי־אִשָּׁ֥ה כֻשִׁ֖ית לָקָֽח׃
米利暗和亞倫因摩西所娶的古實女子,議論摩西的不是,因為他娶了一個古實女子。
Rashi
ותדבר AND [MIRIAM AND AARON] SPAKE — The term דבר in every passage where it is used implies harsh language, for so it states, (Genesis 42:30) “The man, the lord of the land spake (דבר) roughly to us”. The term אמר, however, is always an expression denoting supplication, for so it states, (Genesis 19:7) “And he said (ויאמר) ‘I beg of you (נא), my brethren, do not so wickedly” ; (verse 6 of this chapter) “And He said (ויאמר), Hear, I pray you (נא), My words’ — for the word נא always expresses supplication (Sifrei Bamidbar 99).
Ibn Ezra
"And Miriam spoke": She was [the actual] speaker while Aaron agreed or was silent; therefore he was punished [as well].