Abū Bakr Aḥmad ibn Ḥusayn ibn ʿAlī ibn Mūsā al-Khusrawjirdī al-Bayhaqī (Arabic: أبو بكر أحمد بن حسين بن علي بن موسى الخسروجردي البيهقي, 994–1066), also known as Imām al-Bayhaqī, was a Sunni scholar widely known for being the foremost leading hadith master in his age, leading authority in the Shafi'i school, leading authority on the foundation of doctrine, meticulous, a devoted ascetic and one of the notable defenders of the Ash'ari school. Al-Dhahabi said: "Unequalled in his age, unrivalled amongst his peers, and the Ḥāfiẓ of his time." Source: Wikipedia (en)