Why was God so definitive in regards to His laws and orders to Moses and aaron?

Answer 1

There are actually many answers for this, I will simply key in on a few. The first is that Jews and Christians who desire to live for the God their bible declares is adamant about living according to his view of righteousness, and not according to man's view or understanding of righteousness. Another reason and more directly tied to the two men in the question is that at Sinai, Israel was about to become a nation. So when Torah (instruction/law) was committed to writing, it was to be used as the "judicial system" of the nation of Israel. This is confirmed in Torah when it commands that all future kings were to write a copy of Torah by their own hand and then govern from it. They were to read it to the people every 7 years (during Sukkot) so the people knew the laws and understand how to act and what was expected in their society. So Torah in a sense can be called the "constitution" of the nation of Israel.