Musnad Abu Ya'la al-Mawsili 147:37

Zuhayr narrated to us, Jarir narrated to us, al-Hasan ibn Ubayd Allah narrated to us, from Tha'labah, from Anas ibn Malik, who said: The Messenger of Allah (may Allah bless him and grant him peace) smiled, then said: "I am amazed at the believer; indeed, Allah does not decree a decree for him except that it is good for him."