In the name of Allah, Most Gracious, Most Merciful.
Abu Yahya Suhaib bin Sinan (May Allah be pleased with him) reported that: The Messenger of Allah (May Allah exalt his mention and protect him from imperfection) said: “How wonderful is the case of a believer; there is good for him in everything and this applies only to a believer. If prosperity attends him, he expresses gratitude to Allah and that is good for him; and if adversity befalls him, he endures it patiently and that is better for him”. (Muslim)
Commentary: A Muslim is required to behave in poverty and prosperity, affluence and hardship, in the manner stated in this Hadith. It means that to forget Allah in prosperity, rather than being thankful to Him for His Favour is defiance of His Orders. Similarly, it is unbecoming of a Muslim that in troubles and turmoil, rather than being patient, he tends to weeping and crying, grousing and grieving against the Will of Allah.
Riyaadiss-Saliheen (The Meadows of the Righteous)
By Imam An Nawawi
Chapter 3, Page 14, No 27