4 He is the Rock, his work is perfect: for all his ways are judgement: a God of truth and without iniquity, just and right he is
15 But Jeshurun waxed fat, and kicked: thou art waxen fat, thou art grown thick, thou art covered with fatness; then he forsook God which made him and lightly esteemed the Rock of his salvation.
16 They provoked him to jealousy with strange gods, with abominations provoked they him to anger.
17 They sacrificed unto devils, not to God; to gods whom they knew not, to new gods that came newly up, whom your fathers feared not.
18 Of the Rock that begat thee thou art unmindful, and hast forgotten God that formed thee.
19 And when the Lord saw it, he abhorred them, because of the provoking of his sons, and of his daughtersDeuteronomy 32:4 explains that "the Rock" is the Rock because he is perfect. He is unchanging. He is the foundation upon which all should be built. The chapter then goes on to explain the laziness of the Lord's people and their unwillingness to worship God and find truth. The Lord stirs up His anger against them and they are no longer given the chance to know Him.
What do we learn from this? Eternal law is unchanging. Just because we wish one thing was a different way, that doesn't mean the other is done exactly the same.