Disciples of Aaron
Hillel said: Be of the disciples of Aaron, love peace and pursue peace, love your fellows and bring them close to the Torah. - Avos 1, 12
Aharon Hacohen's obsession with peace has been abundantly commented upon. The mefarshim on the mishna (see Rambam and Rabeinu Yona) cite various examples and stories of how Aharon would go above and beyond any normal social expectations for the sake of promoting peace between neighbors, husband and wife and all of mankind. Aharon Hacohen's attitude towards peace is certainly remarkable and saintly, but this doesn't seem to be the point of the mishna. The mishna is conveying a message, emphasizing a point. It doesn't just tell us to pursue peace and bring people close to the Torah. It says ‘love peace and love mankind in addition to pursuing peace and bringing mankind close to the Torah’. What is the message that Hillel is telling us, and what are these additional sentiments that Hillel is instructing us to possess?
Man left to act to his own devices will likely follow his sentiments, emotions, and passions. This is because one tends not to exert any energy to do something unless he wants to. In other words without an outside force involved, one would simply remain inert. To affect change in attitude one needs a kinetic force. One will not simply pursue peace just because it is a virtue. Acting virtuous is an ordeal. It requires making an effort. One will not put oneself out to bring others closer to Torah without being in some way propelled by some sort of a driving force.
The purpose of being a disciple is to receive guidance from the teacher. Hillel isn't eulogizing Aharon Hacohen; he is instructing us how we are to behave. His overall message is to spread peace and Torah knowledge. However were Hillel simply to put it as such he would be preaching futilely. Hillel is imparting to us the method to acquire this precept. Hillel is telling us to look at Aharon Hacohen as an example. What was it that drove Aharon Hacohen to make peace and spread Torah? It was his illimitable appreciation of peace and his boundless love for mankind. Aharon Hacohen was infatuated with love of peace and mankind, and therefore Aharon Hacohen quested peace and spread Hashem's word whenever, wherever, and however possible.
If we appreciate peace we will seek it, and if we love mankind we will impart to them what we can of Hashem's Divine Words.