Bava Kamma 92: Pray for Mercy on Others' Behalf
Last mishnah of the chapter: When one injures another, and pays compensation, he still isn't forgiven until the victim offers it -- as learned from the interaction between Avraham and Avimelech. At the same time, however, the victim is not allowed to hold a grudge. Also, 17 (18?) teachings or adages that were clearly known in the world that Rabbah bar Mari provides the sources for them in the Torah. Including poverty follows the poor, and if a friend calls you a donkey, prepare a saddle for your back.