Umar II on Knowledge: Action without knowledge is more harmful than good

Sa’id ibn Abdul Aziz reported: Umar ibn Abdul Aziz, may Allah have mercy on him, wrote to the people of Medina, “Whoever worships without knowledge will cause more harm than good. Whoever considers his words part of his deeds will speak little unless it concerns him. Whoever makes the purpose of his religion to indulge arguments, he will frequently change his position.”

Source: Sunan al-Dārimī 308

عن سَعِيد بْن عَبْدِ الْعَزِيزِ قَالَ كَتَبَ عُمَرُ بْنُ عَبْدِ الْعَزِيزِ رحمه الله إِلَى أَهْلِ الْمَدِينَةِ أَنَّهُ مَنْ تَعَبَّدَ بِغَيْرِ عِلْمٍ كَانَ مَا يُفْسِدُ أَكْثَرَ مِمَّا يُصْلِحُ وَمَنْ عَدَّ كَلَامَهُ مِنْ عَمَلِهِ قَلَّ كَلَامُهُ إِلَّا فِيمَا يَعْنِيهِ وَمَنْ جَعَلَ دِينَهُ غَرَضًا لِلْخُصُومَاتِ كَثُرَ تَنَقُّلُهُ

308 سنن الدارمي المقدمة باب من قال العلم الخشية وتقوى الله