After Aarons two sons die, Moses expects the ceremony of dedication to continue. This involved eating from the different sacrifices that comprised the dedication ceremony of the Tabernacle and the installation of Aaron and his two remaining sons Elazar and Itamar. Aaron himself does not know for certain whether he should continue with ceremony of dedication. So, he takes the initiative decides not to eat the sin offering but burnt it instead. An act of recognition of his mourning the loss of his sons.
Moses examines the situation. The Hebrew says “Darosh darash Moshe.” Literally, Moshe looked into the matter. But it could equally mean he used his powers of deduction to decide on what should be done. He concluded there should be no change in laid down procedure. And so, he was angry with Aaron for deviating.
Aaron for his part argue that he had carried out all and every procedure required. But that given his state of mourning for his sons, he felt it appropriate to change the sin offering from one that involved eating, into one that did not in and was completely burnt on the altar. And in this way, he was able to combine his private role with his public role. Not only but he added “Surely God would have approved.”
This exchange is a seminal one in the Torah. Moses is arguing for the law. His logic leads him to one conclusion. This proves the importance of deductive logic in determining Jewish Law. On the other hand, Aaron replies emotionally, that his pain needs to be recognized and he found a way of doing it without distracting from the communal ceremony.
The Torah continually talks about the importance of combining Mishpat, law, with righteousness, Tsedek. Here Moses stood for logical deduction of law, Mishpat. But Aaron stood for emotion, flexibility given the circumstances, Tsedek. Moses agrees. One needs both for a healthy human system that combines order with sensitivity and feeling. And that is how halacha ought to function in its ideal state. Now as much as them.