He who acts without knowledge harms more than benefits.

—‘Umar b. ‘Abd al-‘Azīz [d. 101H/719CE]

[al-Khatib (al-Faqih wa al-Mutafaqqih, 1/19), Ibn ‘Abd al-Barr (Jami Bayan al-‘Ilm, p.54), Ibn Abi Shaibah (al-Musannaf, 13/470)]

(Read on pg 80, Ibn al-Jawzi, Sincere Counsel to the Students of Sacred Knowledge. Daar as-Sunnah Publishers. Birmingham: 2011.)