When Allah commissioned Musa at the burning bush, Musa's first request was not weapons or armies. It was his brother: “And appoint an assistant for me, from my family. Aaron, my brother. Strengthen me with him. And have him share in my mission.” (Quran 20:29-32). Allah granted it in full, making Harun a prophet by his brother's dua, the only prophethood ever given at another prophet's request.
Eloquent where Musa was fiery, Harun stood beside him through every confrontation with Pharaoh, and led Bani Israil when Musa went up Sinai. There he faced the golden calf disaster, pleading with the people, holding the community together without splitting it, until Musa returned. His story is the dignity of the second chair: history's spotlight follows Musa, but the Quran makes sure we know the mission ran on two sets of shoulders.