Abū’l-Ḥusayn ‘Asākir ad-Dīn Muslim ibn al-Ḥajjāj ibn Muslim ibn Ward ibn Kawshādh al-Qushayrī al-Naysābūrī (d. 875 CE) compiled what Sunni Muslims regards as the second most authoritative collection of ḥadīth (accounts of Muḥammad’s words and acts). Muslim travelled extensively searching for accounts. His work also described early Islamic theology and Qurʾānic exegesis. Although not every account in his work is still universally regarded as genuine it provides material that is foundational for studying Islam’s formative period.