Musnad Abu Ya'la al-Mawsili 148:63

Abu Bakr ibn Abi Shaybah narrated to us, Waki' narrated to us, Sufyan narrated to us, from al-Qasim ibn Shurayh, from Abu Bahr, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "How wonderful is the affair of the believer; indeed, Allah does not decree a decree for him except that it is good for him."