In the twenty-second book of Homer's Odyssey, Odysseus begins his battle with the suitors. Aided by his son Telemachus and a few trusty servants, Odysseus slaughters the suitors.
At Odyssey 22.310-377, however, some of the combatants begin to beg Odysseus to spare their lives. The first is Leodes, who claims that he served as the priest among the suitors. Because he was their priest, Odysseus concludes that he must have prayed for Odysseus' death. Therefore, Odysseus kills Leodes.
The next person to supplicate Odysseus is the singer Phemius, who claims that he is a "minstrel who sings for gods and men" and that the "the Suitors dragged me here by force" (A.S. Kline translation). In this case, it is not clear whether Odysseus was moved by Phemius' petition, but, before Odysseus can react, Telemachus intervenes and persuades his father to spare Phemius' life.
Telemachus also convinces Odysseus to spare the life of the herald Medon, "who used to care for me as a child in this house."
Thus, in Odyssey 22, Odysseus spares Phemius and Medon due to the intervention of his son Telemachus.