ENOfficial
‘Abd al-Mālik b. ‘Umair reported in mursal form that God's messenger said, “Fātihat al-Kitāb contains healing for every disease.” Dārimī and Baihaqi, in Shu'ab al-īmān, transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ عَبْدِ الْمَلِكِ بْنِ عُمَيْرٍ مُرْسَلًا قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «فِي فَاتِحَةِ الْكِتَابِ شِفَاءٌ مِنْ كُلِّ دَاءٍ» . رَوَاهُ الدَّارمِيّ وَالْبَيْهَقِيّ فِي شعب الْإِيمَان
sunnah.com