Musnad Ahmad 1575

It was narrated from "Umar bin Sa"d that his father said: The Messenger of Allah (ﷺ) said: "I am amazed at [the situation of] the believer: if something good befalls him, he praises his Lord and gives thanks, and if calamity strikes him, he seeks reward with his Lord and bears it with patience. The believer will be rewarded for everything, even the morsel he lifts to his mouth."