Deutéronome 33:8

And Mosheh the prophet blessed the tribe of Levi, and said, With Perfections and Lights hast Thou robed Aharon, the man whom Thou didst find devout before Thee, whom Thou didst try in the temptation, and he was sincere, and didst prove at the Contention Waters in Rekem, and he was found faithful.

Of Levi [literally: to Levi] he said He said to God , concerning Levi. Compare, “Say concerning me, ‘He is my brother’” [Genesis 20: 13].

for Your pious one the man who is pious for You.

whom You tested at Massah this last word here has the sense of a common noun, meaning “a test”. The verse thus is rendered as follows: He is a pious one, in whom there has been found no fault, except for the matter of Merivah, over which he has already been punished. This also strengthens my explanation concerning the matter of the golden calf, that he made it for the glory of God [comment on Exodus 31: 18].

Your Tumim and Your Urim will forever be his, and his descendants’.

UL’LEIVI’ HE SAID - “and ‘of’ Levi means “and ‘to’ Levi.” But Rashi translates the prefix lamed here, as “of.” he said.” This is Rashi’s language, and it is also the opinion of the commentators. It is like the expressions: say ‘li’ (of me):. he is my brother;, literally: “to me,” is interpreted as “of me.” and the men of the place asked him ‘l’ishto’ (about his wife)., 26:7. Here also, the word l’ishto, literally: “to his wife,” means “of his wife.” There are many such examples. In my opinion [the expression here is to be understood literally: “and ‘to’ Levi he said”] because Moses had mentioned the names of Reuben and Judah in his blessing [of them], saying, Let Reuben live, the voice of Judah, but he did not mention the names of the other tribes in [the text of] their blessings. Therefore Scripture states, And to Levi he said, To Benjamin he said [in order to make it clear to whom he was addressing his blessing]. This indicates that the tribes were facing him [Moses], and he called Levi and put his eyes upon him and said, thy Thummim and thy Urim. Similarly he blessed each tribe face to face.

תומיך ואוריך לאיש חסידך, Moses refers to G’d having given to Aaron who was the outstanding member of the tribe of Levi, the pious tribe, the urim and tumim lodged within his breastplate pouch. The Talmud Yuma 73, derives from the above that any priest who speaks with holy spirit is of the calibre that when he employs the urim and tumim to address enquiries to G’d, he will receive G’d’s answer to such enquiries. Hence the word “איש,” a man of lofty spiritual standing, as if to underscore that character trait.

אשר נסיתו במסה, Moses reminds G’d that in all the various tests (Numbers 14,22) that the Jewish people had subjected Him to, the tribe of Levi had never been a participant in such demonstrations of lack of faith. This was also why the decree which G’d imposed on the generation of the spies did not apply to them, and the Levites that were of age at that time did not die in the desert.

תריבהו על מי מריבה, You have challenged them at the waters of strife, as a result of which You deprived the people of the two outstanding heads of the tribe of Levi.