Musnad Ahmad 529:9

Hisham ibn Sa'id narrated to us, al-Hasan ibn Ayyub al-Hadrami narrated to us, he said: 'Abdullah ibn Nasih al-Hadrami narrated to us, from 'Utbah ibn 'Abd al-Sulami, that the Prophet, peace and blessings of Allah be upon him, said to his companions: "Stand up and fight." He said: Then a man was struck by an arrow. He said: The Prophet, peace and blessings of Allah be upon him, said: "This one has made [Paradise] obligatory [for himself]."