After Korah and two hundred fifty men rebelled against Moses, Aaron, and ultimately the Lord, accusing Moses of taking too much upon himself, the Bible says,

Then Moses was very angry, and said to the Lord, “Do not respect their offering. I have not taken one donkey from them, nor have I hurt one of them” (Numbers 16.15).

Moses could speak before the Lord with a good conscience, knowing that he had never taken anything from them, nor had he harmed them in anyway. Therefore, their criticism of him had no validity.