Rashi: "le'Levi" means (not 'to the B'nei Levi', but) 'about the B'nei Levi'. ¹

Ramban: Moshe actually stated the blessing to Levi (as well as to each of the tribes) directly - Having mentioned Reuven and Yehudah by name in their actual B'rachos, ² but not the other tribes, the Torah informs us here that Moshe called Levi - and each of the tribes, to come and stand before him, in order to bless them face to face.

Rashi, Tarfgum Onkelos and Targum Yonasan: It refers to the Urim ve'Tumim of the Shechinah.

Panim Yafos: It refers to the Avos. The Gematriya of "Urim" (including the word itself) is two hundred and forty-eight - like that of Avraham. The Gematriya of 'Or' (including the word itself) is two hundred and eight - like that of Yitzchak, whereas "Tumecha" hints at Ya'akov, who is called "Ish Tam".

Oznayim la'Torah: Because whereas everywhere else the Torah is referring to the Urim ve'Tumim regarding the person, where first the letters light up and then the Kohen Gadol arrives at the correct answer, here is referring to the Urim ve'Tumim regarding Hashem - who first decides what the answer will be and then lights up the letters on the Choshen. ¹

Refer to 33:8:2:2. In Bereishis 25:27. The order is inverted ("Tumecha" is mentioned first) because the Torah often lists the Avos in the reverse order - as in Bechukosai Vayikra, 26:42 "ve'Zacharti es Berisi Ya'akov

Targum Onkelos and Targum Yonasan: It refers to Aharon.

Seforno and Hadar Zekenim and Rosh: It refers to the tribe of Levi all of whom were pious, since they did not sin by the Chet ha'Eigel, and of whom Aharon was the head. ¹

Rashi: He is referring to Masa u'Merivah, where Yisrael complained that they had no water, ¹ but the tribe of Levi did not take part..

Rashi #2, Targum Onkelos and Targum Yonasan: He is referring to when Moshe struck the rock - because although Aharon was punished, he did not participate in the sin. ²

Seforno: He is referring to all the times that Yisrael tested Hashem, ³ in which the tribe of Levi never participated.

Ramban (citing the Ibn Ezra): He is referring to all the times that Hashem tested Aharon, all of which Aharon passed with flying colors, ⁴ with the exception of Mei Merivah

Rashi #1 (citing Targum Onkelos) and Targum Yonasan: 'You tested him ¹ at Mei Merivah and he proved himself faithful'.

Rashi #2 (citing the Sifri): You came with a pretext against [two leaders of the tribe of Levi] at Mei Merivah. ²

Ramban #1 (citing the Ibn Ezra): Refer to 33:8:5:3. ³

Ramban #2: 'You quarreled with him (took him to task) ⁴ for the punishment that was due to Yisrael ⁵ who quarreled with Hashem'. ⁶

Oznayim la'Torah: It is referring to the sin of Mei Merivah, where Aharon did not really sin, yet he remained silent and did not challenge the harsh decree in his own self-defence.

Moshav Zekenim: Moshe cast the ashes of the Eigel into water, which he made Yisrael drink. It was 'Mei Merivah' for those who sinned - but not for Levi who were totally innocent. Also by 'Mei Merivah' here, Levi ¹ was totally innocent,

Lev Eliyahu (Sh'mos p.99): Hashem tested all of Yisrael; only Levi was totally faithful (Avos d'R. Nasan 34). The entire generation were Tzadikim). ² Fortunate is the generation whose sins are numbered (ten sins in forty years, and some of those were attributed to individuals, such as leaving over the Manna!