Variantly (Devarim, Ibid.): "And of Levi, he said: "Your tumim and your urim (are destined) for (Aaron) the man of Your lovingkindness
(i.e., the man who practiced lovingkindness with Your children.
"whom You proved in Massah": You proved him with many trials, and he was found "complete" in all of them.
"You 'embattled' him at the waters of contention" (viz. Bamidbar 20:10-13): You caught him in the toils of libel. (If) Moses said (Ibid. 10) "Hear, now, you fractious ones," what did Aaron and Miriam do? (i.e., what sin did they commit which kept them from entering Eretz Yisrael?)