Numbers 12
Presumably, Miriam had started these accusations and probably instigated her brother Aaron to follow suit.
Numbers 12:3 categorically mentions the greatest character trait of Moses - (Now Moses was very humble—more humble than any other person on earth.
As a humble man, Moses would be open to correction. He was not one that loved to Lord it over his subjects. Initially, he even tried to run away from the call of God as he was not confident because he stammered.
The words of Miriam were full of disdain and contempt. Miriam was hiding behind patriotism and loyalty to God's commands, and yet she was opposing God's ordained leader.
She even went a step further to through comparison prove that Moses was not better than Aaron or her. Truth is, Moses had never regarded himself better than them. When God gave Moses the chance to be solely exalted , he disapproved.
Then the Lord said, “I have seen how stubborn and rebellious these people are. 10 Now leave me alone so my fierce anger can blaze against them, and I will destroy them. Then I will make you, Moses, into a great nation.” Exodus 32:9-10.
Rather, Moses interceeded for God to turn from His anger towards all Israel. So why would Miriam after knowing all these things about her brother still go ahead to say all these unpleasant things?
WHAT IS NEXT?