Sayyiduna Usamah bin Sharik (may Allah be pleased with him) said: I was with the Prophet (peace and blessings be upon him) when Bedouins came and asked: What is the best thing that people have been given? He (peace and blessings be upon him) said: Good character. They said: O Messenger of Allah, should we seek medical treatment? He (peace and blessings be upon him) said: "Yes, O servants of Allah, seek treatment, for Allah, the Mighty and Majestic, has not placed any disease on earth without also placing its cure, except for one disease." They said: What is it? He (peace and blessings be upon him) said: "Old age."
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 462