Musnad Ahmad 8:54

'Abd al-Razzaq narrated to us, Ma'mar informed us, from Abu Ishaq, from al-'Aizar ibn Hurayth, from 'Umar ibn Sa'd ibn Abi Waqqas, from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I am amazed by the believer. If good befalls him, he praises Allah and is grateful. And if a calamity befalls him, he praises Allah and is patient. So the believer is rewarded in all his affairs, even to the point that he is rewarded for the morsel he lifts to the mouth of his wife."