Musannaf Ibn Abi Shayba 33:52

Affan ibn Muslim narrated to us, he said: Mubarak narrated to us, from al-Hasan, that the Prophet Dawud, may Allah bless him and grant him peace, said: "O Allah, [grant me] neither an illness that weakens me, nor a state of health that makes me forget, but [something] between the two."