John Calvin on Numbers 21:5

5. And the people spake against God and against Moses. Either because they murmured against God in the person of Moses, or else because their impiety broke forth to such a furious extent, that they openly blasphemed against God; and this latter opinion is most in accordance with the words, because by their use of the plural number they accuse two parties together. Addition in Fr., “sinon qu’ils s’addressent aussi a Aaron;” unless they also address Aaron. But, inasmuch as Moses had nothing separate from God, no one could enter into a contest with him without warring also against God Himself. Here, however, as I have said, their insolence proceeded still further, so as not only to rail against the minister, but to vomit forth also their wicked blasphemy against God Himself, as if He had injured them most grossly by their deliverance.