Allah has not sent down any disease except that He has also sent down the cure for it Sunan Ibn Majah 3436
Arabic hadith text
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَهِشَامُ بْنُ عَمَّارٍ، قَالاَ حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنْ زِيَادِ بْنِ عِلاَقَةَ، عَنْ أُسَامَةَ بْنِ شَرِيكٍ، قَالَ شَهِدْتُ الأَعْرَابَ يَسْأَلُونَ النَّبِيَّ ـ صلى الله عليه وسلم ـ أَعَلَيْنَا حَرَجٌ فِي كَذَا أَعَلَيْنَا حَرَجٌ فِي كَذَا فَقَالَ لَهُمْ " عِبَادَ اللَّهِوَضَعَ اللَّهُ الْحَرَجَ إِلاَّ مَنِ اقْتَرَضَ مِنْ عِرْضِ أَخِيهِ شَيْئًا فَذَاكَ الَّذِي حَرَجٌ " . فَقَالُوا يَا رَسُولَ اللَّهِ هَلْ عَلَيْنَا جُنَاحٌ أَنْ نَتَدَاوَى قَالَ " تَدَاوَوْا عِبَادَ اللَّهِ فَإِنَّ اللَّهَ سُبْحَانَهُ لَمْ يَضَعْ دَاءً إِلاَّ وَضَعَ مَعَهُ شِفَاءً إِلاَّ الْهَرَمَ " . قَالُوا يَا رَسُولَ اللَّهِ مَا خَيْرُ مَا أُعْطِيَ الْعَبْدُ قَالَ " خُلُقٌ حَسَنٌ "
Translation
It wasnarrated that Usamah bin Sharik said
“I saw the Bedouinsaskingthe Prophet (ﷺ): ‘Is there any harm in such and such, isthereany harm in such and such?’ He said to them: ‘O slaves of Allah!Allah has only made harm in that which transgresses the honor ofone’sbrother. That is what is sinful.’ They said: ‘O Messengerof Allah! Isthere any sin if we do not seek treatment?’ He said:‘Seek treatment,O slaves of Allah! For Allah does not create anydisease but He alsocreates with it the cure, except for old age.’They said: ‘O Messengerof Allah, what is the best thing that aperson may be given?’ He said:‘Good manners.’”