The Iliad/Book 18

Antilochus, a messenger, rushes to tell Achilles that Patroclus has died. Upon noticing that Hector is wearing Patroclus' armor he breaks down with grief. Antilochus joins him and Achilles lets out a "wrenching cry". Thetis and a group of immortal sea-nymphs join Achilles in mourning and she (Thetis) proclaims that eventhough her son was born flawless, there is nothing she can to do ease the pain of a lost friend. Then Thetis and Achilles have a conversation where she tells him not to hold his anguish inside and she also informs him that "...hard on the heels of Hector's death your death must come...". Achilles regains his rage and asks his mother not to restrain him from fighting. She suggests that he not fight until she comes back the next day.