"The Messenger of Allah (saas) said: 'There is no supplication that a person can say that is better than: Allahumma inni as'aluka al-mu'afah fid-dunya wal-akhirah (O Allah, I ask You for Al-Mu'afah in this world and in the Hereafter).'"
Sunan Ibn Majah Book 34, Hadith 25