ENOfficial
It was narrated from'Amrbin shu'aib, from his father that his grandfather said: "the Messenger of Allah (ﷺ) said: 'Whoever practices medicine when he is not known for that, he is liable.(Daif)
Source: sunnah.com
Other translations
Arabic
أَخْبَرَنِي عَمْرُو بْنُ عُثْمَانَ، وَمُحَمَّدُ بْنُ مُصَفًّى، قَالاَ حَدَّثَنَا الْوَلِيدُ، عَنِ ابْنِ جُرَيْجٍ، عَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ تَطَبَّبَ وَلَمْ يُعْلَمْ مِنْهُ طِبٌّ قَبْلَ ذَلِكَ فَهُوَ ضَامِنٌ " .
sunnah.com