In 10 A.H. when Najran was conquered by the Muslims, the Holy Prophet (SAWS) appointed his companion ‘Amr ibn Hazm as governor of the province of Yemen. At this time the Holy Prophet (SAWS) dictated a detailed book to Ubayy ibn Ka’b and handed it over to ‘Amr ibn Hazm.
This book, besides some general advices, contained the rules of Shari’ah about purification, Salah, Zakah, Ushr, Hajj, Umrah, Jihad (battle), spoils, taxes, Diyah (blood money), administration, education etc.
Sayyiduna Amr ibn Hazm performed his functions as governor of Yemen in the light of this book. After his demise this document remained with his grandson, Abu Bakr, Imam Zuhri learnt and copied it from him. He used to teach
it to his pupils.