In his early days he wrote down narrations from Hushaym and others, but when he later began compiling books he found it necessary to take reports from Yaḥyā ibn Ṣāliḥ and Hishām ibn ʿAmmār. (1)

The weakest of his works is Kitāb al-Amwāl. He will approach a chapter that contains thirty hadiths and fifty foundational texts traced back to the Prophet ﷺ, yet he cites only one or two traditions—both drawn from the Syrian corpus—and then proceeds to analyze their wording. None of his other books rivals Gharīb al-Muṣannaf. (2)

One day, after finishing the prayer, he passed by the house of Isḥāq al-Mawṣilī. People said to him, “Abū ʿUbayd, the owner of this house says that your book Gharīb al-Muṣannaf contains a thousand faulty letters.” He replied, “In a work that runs to more than one hundred thousand letters, the presence of a mere thousand errors is hardly excessive! Perhaps Isḥāq possesses one recension and we possess another; unaware of this, he judged us mistaken, whereas both versions are sound. And perhaps he erred in a few letters and we erred in a few letters—the total error remains trifling.” (3)

As for the book Gharīb al-Ḥadīth, it contains fewer than two hundred instances where he says, “I heard,” while the rest is “al-Aṣmaʿī said,” or “Abū ʿAmr said.” It also includes forty-five hadiths that have no basis; Abū ʿUbayd accepted them on the authority of Abū ʿUbayda Maʿmar ibn al-Muthannā. (4)

Al-Khaṭīb (5) said—in the isnād conveyed to us by Ibn ʿAllān: al-Kindī informed us, from al-Shaybānī, from him; ʿAlāʾ ibn Abī al-Mughīrah narrated to me, and ʿAlī ibn Baqāʾ (6) informed us,