Why does the Torah add the (otherwise superfluous) word "Va'yitz?ak Moshe el Hashem Leimor"?
Rashi: Because Moshe was asking Hashem to inform him whether He would answer him or not. 1
Rashi: Which Hashem did in the following Pasuk. In fact, this is one of four places where Moshe asked Hashem for a reply to his request: : 1. In Va'eira Sh'mos, 6:12; 2. Here; 3. In Pinchas, 27:15, 4. In Va'eschanan Devarim, 3:23. See Oznayim la'Torah.
Why did Moshe begin his Tefilah with the words "Keil Na"?
Rashi: To teach us that, when making a request of one?s friend, one should introduce it with two or three words of supplication.
Why did Moshe repeat the word "Na"?
Targum Onkelos and Seforno: The first "Na" means 'please', the second one, 'now' (so that we should not need to shame her by sending her out of the camp ? Seforno).
Targum Yonasan: ??Please have compassion O G-d of compassion; please O G-d who rules over the souls of all flesh, please 1 cure her!?
It is not clear shy he adds a third ?please?.
Why did Moshe Daven such a short Tefilah for Miriam?
Rashi #1: So that people should not say accusingly 'His sister is suffering and he is Davening so long!' 1
Rashi #2: So that people should not say accusingly that for his sister he Davens a long Tefilah, but for them he wouldn't do that! 2
Some ssituations call for a long Tefilah, and some, for a short one. See Torah Temimah, note 13, who elaborates.
In spite of the fact that he Davened for Yisrael for forty consecutive days after the sin of the Golden Calf (See Eikev Devarim, 9:25).
Why did Moshe not mention Miriam by name?