John Wesley on Deuteronomy 33:9

I have not seen him - That is, I have no respect unto them. The sense is, who followed God and his command fully, and executed the judgment enjoined by God without any respect of persons, Exo 32:26,27. They kept thy covenant - When the rest broke their covenant with God by that foul sin of idolatry with the calf, that tribe kept themselves pure from that infection, and adhered to God and his worship.