Abdullah ibn Mas’ud reported: I saw the Messenger of Allah, peace and blessings be upon him, tell the story of a prophet who was beaten by his people and he wiped the blood from his face, saying, “My Lord, forgive my people for they do not know.” 

Source: Sahih Bukhari 6530, Sahih Muslim 1792

Grade: Muttafaqun Alayhi (authenticity agreed upon) according to Al-Bukhari and Muslim