Abu Dawud Book 22, Hadith Number 3846.

Narated By Usamah ibn Sharik : I came to the Prophet (PBUH) and his Companions were sitting as if they had birds on their heads. I saluted and sat down. The desert Arabs then came from here and there. They asked: Apostle of Allah, should we make use of medical treatment? He replied: Make use of medical treatment, for Allah has not made a disease without appointing a remedy for it, with the exception of one disease, namely old age.