The Gemara (Arachin 15a) counts this as one of the ten Nisyonos that our forefathers tested Hashem in the wilderness (see Avos 5:4). What is their sequence; and why are they called "tests," rather than "sins"?
Maharal (Derech Chayim to Avos 5:4): The Gemara in Arachin 15a lists the ten in sets of five pairs. 1 A 'Nisayon,' like a 'Nes' (miracle), means a departure from natural world order. Such conduct was not befitting of us, after all of the kindnesses that Hashem did for us. It was the merit of Avraham's ten Nisyonos that now protected Yisrael.
Maharal: Two at the Sea, two regarding water, two regarding the Manna, two regarding the Selav, the Egel, and [the spies at] Midbar Paran. We find that the number 10 is commonly divided as 2 sets of five, or 5 sets of 2.
QUESTIONS ON RASHI
Rashi writes: "Museinu - ... This is not a noun ('our death'), [but rather a verb] ... 'we were to die.' Targum Onkelos translates as 'Levai d'Misena,' just like [the Targum to] 'Lu Masnu' (Bamidbar 14:2)." What is Rashi demonstrating by bringing the Targum?
Gur Aryeh: The Targum shows clearly that "Museinu" is not a noun, but rather a verb, 1 meaning "if only we had died" - just like it means in Bamidbar.
Gur Aryeh: Only that here the verb "Museinu" is in the infinitive, a contraction of "la'Mus Anachnu," thus the vowel Shuruk. In Bamidbar, the verb is in simple past tense, so it is "Masnu" with a Patach.