Musnad Ahmad 1017:96

Muhammad ibn Ja‘far and Rawh—the meaning is the same—said: ‘Awf narrated to us, from Maymun Abu ‘Abd Allah—Rawh said: “The Kurd”—from ‘Abd Allah ibn Buraydah, from his father, Buraydah al-Aslami, who said: When the Messenger of Allah (may Allah bless him and grant him peace) arrived at the fortress of the people of Khaybar, the Messenger of Allah (may Allah bless him and grant him peace) gave the banner to ‘Umar ibn al-Khattab, and those who rose from the Muslims rose with him. They met the people of Khaybar, and the Messenger of Allah (may Allah bless him and grant him peace) said: “I shall certainly give the banner tomorrow to a man who loves Allah and His Messenger, and whom Allah and His Messenger love.” When the next day came, he called for ‘Ali, who was suffering from an eye ailment, so he spat into his eyes and gave him the banner. The people rose with him and met the people of Khaybar. Suddenly, Marhab was reciting verses before them, saying: “Khaybar knows that I am Marhab, Fully armed, a tested hero. I thrust at times, and at times I strike, When the lions approach, blazing with rage.” He said: He and ‘Ali exchanged two blows. He struck him on his crown until the sword bit into his molars, and the people of the camp heard the sound of his strike. He said: The last of the people had not yet caught up with ‘Ali before victory was granted to him and to them.