Adam Clarke on Deuteronomy 32:4

He is the Rock - The word צור tsur is rendered Creator by some eminent critics; and khalyk is the reading in the Arabic Version. Rab. Moses ben Maimon, in his valuable work, Moreh Nebochim, observes that the word צור tsur, which is ordinarily translated rock, signifies origin, fountain, first cause, etc., and in this way it should be translated here: "He is the first principle, his work is perfect." As he is the cause of all things, he must be infinitely perfect; and consequently all his works must be perfect in their respective kinds. As is the cause, so must the effect be. Some think the word rock gives a very good sense: for, as in those lands, rocks were the ordinary places of defense and security, God may be metaphorically represented thus, to signify his protection of his followers. I prefer the opinion of Maimon.