Musnad Ahmad 8:136

Waki’ narrated to us, Isra’il narrated to us, from Abu Ishaq, from al-’Aizar ibn Hurayth al-’Abdi, from ‘Umar ibn Sa’d, from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I am amazed at the believer; if good befalls him, he praises Allah and is grateful, and if a calamity befalls him, he seeks reward and is patient. The believer is rewarded for everything, even for the morsel he raises to his mouth."