Musnad Abu Ya'la al-Mawsili 152:115

Abu Khaythama narrated to us, Jarir narrated to us, from ‘Ata’ ibn al-Sa’ib, from Abu Wa’il, from Abu ‘Abd al-Rahman, from ‘Abdullah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, Allah has not sent down a disease except that He has created a cure for it; those who know it know it, and those who are ignorant of it are ignorant of it."