Muwatta Malik, Book 54, Hadith 1792 (In-Book)

Malik related to me that he heard that the Messenger of Allah, may Allah bless him and grant him peace, said, "If there is a remedy that will reach the disease, then cupping will reach it."

وَحَدَّثَنِي مَالِكٌ، أَنَّهُ بَلَغَهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ إِنْ كَانَ دَوَاءٌ يَبْلُغُ الدَّاءَ فَإِنَّ الْحِجَامَةَ تَبْلُغُهُ ‏" ‏ ‏.‏

sunnah.com

also referenced under: Book 54, Hadith 27 (USC-MSA)