Musnad Ahmad 1118:20

Mu'awiyah ibn 'Amr narrated to us, Rushdin narrated to us, he said: Ibn Hani' al-Khawlani narrated to me, that 'Amr ibn Malik narrated to him, that he heard Fudalah saying: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Every dead person has his deeds sealed, except for the one who guards the frontier in the way of Allah; his reward continues to flow for him until the Day of Resurrection, and he is protected from the trial of the grave."