Musnad Ahmad 30:3626

'Abd al-Samad and Abu 'Amir narrated to us, they said: Hisham narrated to us, from Yahya, from Abu Ja'far, from Abu Hurayrah, he said: Abu 'Amir said: I heard Abu Hurayrah say: The Messenger of Allah, peace and blessings of Allah be upon him, said: "The best of deeds in the sight of Allah, the Almighty and Majestic, is: faith in which there is no doubt, a military expedition in which there is no misappropriation of spoils, and an accepted Hajj."