The Prophet (peace and blessings be upon him) said:
"Medicine is also part of the divine decree, and it benefits whomever Allah wills with whatever He wills."
Hadith Referenceصحیح الجامع الصغیر / حرف الدال / 3416
Hadith Gradingالألبانی:حسن
Hadith Takhrij[ابن السني] عن ابن عباس. مشكلة الفقر ١١.