It is very surprising that Aharon would betray his brother Moshe and decide to make the Eigel HaZahav. When Moshe asks Aharon why he did so, Aharon responds (Shemot 32:22-24), “Al Yichar Af Adoni Ata Yadata Et HaAm Ki VeRah Hu VaYomeru Li ‘Asei Lanu Elohim Asher Yeilechu Lefaneinu Ki Zeh Moshe HaIsh Asher He’elanu MeiEretz Mitzrayim Lo Yadanu Meh Hayah Lo’ VaOmar Lahem LeMi Zahav Hitparaku VaYittenu Li VaAshlicheihu VaAish VaYeitzei HaEigel HaZeh,” “Please, my master [Moshe], do not get angry. You know these people are evil-bound. They asked me, ‘Make us a god before us in place of Moshe, for we do not know what happened to him.’ I told them to give me any gold they possessed. They removed it and gave it to me, I drew it into the fire, and this calf emerged.” Rashi explains that when the Pasuk states, “and this calf emerged,” it means that Aharon did not know that it would become the Eigel HaZahav. In this case, why did Aharon ask for gold in the first place? What was his intended purpose for the collected gold?
The Sheim MiShmuel explains that Moshe’s absence from Bnei Yisrael caused a great nationwide crisis. However, what was so important about Moshe that without him havoc erupted? Moshe managed to unite the whole nation as one. Without him there was no unity or harmony. Aharon understood this, and wished to calm Bnei Yisrael by emulating Moshe. Consequently, he commanded everyone to partake in a community-wide event to unite Bnei Yisrael. The primary issue with this plan was that certain people were not interested in unity, and were more focused on causing trouble. This group was known as the Eirev Rav, the Nochrim who had joined Bnei Yisrael during Yitziat Mitzrayim.
A proof of Aharon’s good intentions was Hashem’s subsequent reward to him—delegating him as the Kohein Gadol as a result of Midah KeNeged Midah, a fitting reward for his actions. Since Aharon intended to unify the people at Cheit HaEigel, he was appropriately rewarded the position of Kohein Gadol, a position which unifies Bnei Yisrael in their service of Hashem.
One of the important lessons we learn from this incident is the great impact, positive or negative, individuals can have on ther peers. Sometimes, we may act selfishly and not contemplate our actions’ impact on others. Our actions’ potency is manifested by the episode of Cheit HaEigel. Aharon’s actions of unifying the community were successful at first, and carried out with the proper objective (thus meriting his reward). However, when the Eirev Rav interrupted and corrupted Aharon’s intentions, they managed to persuade Bnei Yisrael to commit a sin great as Cheit HaEigel. Therefore, we see how our deeds can alter an entirely benign action to a hostile exploit.