What the Bible says about Meaningless Sacrifices
(From Forerunner Commentary)
The thought here is similar to Isaiah 59:1-2: God has set His will against something that He has commanded. Did He not command the sacrifices? Yes, He did. They are a significant part of the book of Leviticus, and there are some of them in the book of Deuteronomy. He has commanded the people to sacrifice, and indeed, they are sacrificing, but now He comes back and tells them, "They do not mean a thing to Me."
It is not really that the sacrifices mean nothing to Him. Rather, the problem is with the people making the sacrifices; they cause them to be meaningless, both to God and to them, even as their prayers are meaningless. So He has set His will not to accept the offerings they are making.