Usama ibn Sharik said, "I was with the Prophet, may Allah blesshim and grant him peace, when some bedouins came. There were many peopleon all sides. The people were silent and no one spoke except them. Theysaid, 'Messenger of Allah! We experience difficulty in such-and-such andsuch-and-such' and it was in things which are not harmful to people. Hesaid, 'Servants of Allah! Allah has removed difficulty except in a casewhere a man slanders someone unjustly - that is the one who is in difficultyand destroyed.' They said, 'Messenger of Allah, can we make use of medicaltreatment?' 'Yes, servants of Allah,' he replied, 'you can make use ofmedical treatment. Allah Almighty did not create an illness but that Hemade a cure for it - except for one disease.' They asked, 'And whatis that, Messenger of Allah?' 'Old age,' he replied. They said, 'Messengerof Allah, what is the best thing that a man can be given?' 'Good character,'he replied.'"
English reference: Book 14, Hadith 291
Arabic reference: Book 1, Hadith 291