His name was Yusuf ibn 'Abdullah ibn Muhammad ibn 'Abdu'l-Barr an-Nimari the Hafiz, the shaykh of the scholars of Andalusia and the great one of its hadith scholars in his time, and the one there with the greatest memory of the Sunna. His father was already mentioned. During the revolt, he travelled from his home, Cordoba, to the west of Andalusia and then he moved from it to the east of Andalusia where he alternated between Denia, Valencia and Shatiba.
Our shaykh Abu 'Ali al-Ghassani said: "Abu 'Umar, our shaykh, was from an-Namir ibn Qasit in Rabi'a of the people of Cordoba, and he studied there and learned fiqh with Abu 'Umar ibn al-Makawi. He devoted himself to Abu'l-Walid ibn al-Fardi the Hafiz, and from him much of his knowledge of the men (the transmitters) and hadith was taken, and this science was what dominated him. He understood the knowledge of the Qur'an and he listened to Sa'id ibn Nasr, 'Abdu'l-Warith ibn Sufyan, Ahmad ibn Qasim al-Bazzar, Abu Muhammad ibn Asad, Khalaf ibn Sahl the hafiz, Abu Muhammad 'Abdu'l-Mu'min, Abu Zayd 'Abdu'r-Rahman ibn Yahya, Sa'id ibn al-Qazzaz, Abu Zakariyya al-Ash'ari, Abu 'Umar al-Baji, Abu'l-Qasim ibn Abi Ja'far, and Ibn al-Jassur.
He had an ijaza from Abu'l-Fath ibn Shibakht and 'Abdu'l-Hayy ibn Sa'id. He did not travel. A lot of people listened to him, including most of the people of knowledge, and the famous shaykhs: Abu'l-'Abbad ad-Dala'i, Abu Muhammad ibn Abi Quhafa, and Abu Muhammad ibn Hazm, Abu 'Abdullah al-Humaydi, and Tahir ibn Mafuz listened to him, and to our shaykhs Abu 'Ali al-Ghassani, Abu Bakr Sufyan ibn al-'Asi, and he is the last of those esteemed to relate from him.
Praise for him
Abu 'Ali al-Jayani said: "Abu 'Umar was steadfast in seeking knowledge and assiduous in it, and he was masterly and more skilled than those who before him in Andalusia. Abu 'Umar was very renowned throughout Andalusia. People travelled to him and listened to him and he wrote many useful books which went to all areas. Abu 'Ali said that he heard Abu 'Umar say, "There is no one in our land with more fiqh than Qasim ibn Muhammad ibn Qasim and Ahmad ibn Khalid." Abu 'Ali said, "I say that Abu 'Umar was not less than them, nor behind them. He had precedence in the knowledge of tradition, insight into fiqh and the meanings of hadith and he had extensive knowledge of lineage and history."
Concerning his books
Abu 'Umar wrote a book on the Muwatta' entitled the Kitab at-Tamhid about the meanings and isnads in the Muwatta' which is in 20 volumes. It is a an unrivalled book in its method. He wrote al-Istidhkar on the schools of the schools of the cities about what the Muwatta' contains of the meanings of opinion and traditions. There is the Kitab at-Taqassi on the hadiths of the Muwatta', the Kitab al-Isti'ab on the names of the Companions, the Jami' Bayan al-'Ilm, Kitab al-Anbah on the tribes of the transmitters, Kitab al-Intiqa' on the virtues of the three fuqaha': Malik, ash-Shafi'i and Abu Hanifa, the Kitab al-Bayan on the recitation of the Qur'an, the Kitab Bahja al-Majalis wa Uns al-Majalis, and the Kitab Asma' al-Ma'rufin on those known by their kunya in seven volumes. There al-Kafi on fiqh and the disageement in the positions of Malik and his people in 20 books, ad-Duraron the summary of the raids and expeditions, the Kitab al-Qasd wa'l-Umam on the definition of the lineage of the Arabs and non-Arabs, The First of the Nations to speak in Arabic, Testimony to the Affirmation of the Single Tradition, al-Bustan, and Answers on Rare Questions. He has al-Iktifa' on the readings of the Qur'an, Kitab at-Tajwid, a summary of at-Tamyiz by Muslim, Kitab al-Ansaf about the disagrement regarding the basmala, and a summary of the history of Ahmad ibn Sa'id, al-Ishraf on the Shares and other small books.
Abu 'Umar described the Kitab at-Tamhid:
The conversant of my heart for thirty years
and the the polisher of my mind reliever of my care –
The words of your Prophet explained it for you
since his meanings contain fiqh and knowledge.
It contains adab by which one is guided
to piety and fear of Allah and it forbids injustice.
He was born in 368 in Rabi' al-Akhir. He died in Shatiba in Rabi'l-Akhir in 463.