פירוש על במדבר 12:1

ותדבר AND [MIRIAM AND AARON] SPAKE — The term דבר in every passage where it is used implies harsh language, for so it stales, (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).

ותדבר מרים במשה, Miriam uttered criticism of Moses, etc. It is possible that Miriam and Aaron spoke in Moses' presence. Logic would dictate that this was indeed the case. Had they only been talking amongst each other, what difference would it have made to Moses? We must assume therefore that they said what they did as a rebuke to Moses. I believe Sifri confirms my opinion as the author quotes the words: וישמע ה׳ והאיש משה as belonging together, i.e. Moses too heard what Miriam said.

הכושית, from one of the tribes going back to Cham.