Abu Ahmad ibn Adi al-Jurjani: I do not know of any Munkar narration from Abu Mas'ud, and he is among the people of truth and حفظ
Abu al-Shaykh al-Isbahani: One of the great Huffaz
Abu Bakr ibn Abi Shaybah: The most memorizing I have seen in the world are three: Abu Mas'ud, Abu Zur’ah and Ibn Warra
Abu Hatim ibn Hibban al-Busti: He was among those who traveled, collected, compiled, memorized, narrated, and was persistent in adhering to and defending the Sunnah
Abu 'Abd Allah al-Hakim al-Naysaburi: Trustworthy
Abu 'Urubah al-Harrani: Abu Mas'ud is counted among Abu Bakr ibn Abi Shaybah in memorization and Ahmad ibn Sulayman al-Rahwi in scrutiny
Abu Nu'aym al-Isbahani: One of the leading Imams and Huffaz
Ahmad ibn Hanbal: There is no one under the sky who memorizes the narrations of the Messenger of Allah, may Allah bless him and grant him peace, better than Abu Mas'ud, and once he said: Write from him, for he is truthful in speech
Ibn Hajar al-'Asqalani: Trustworthy Hafez, he was criticized without basis
Ibn 'Asakir al-Dimashqi: One of the leading trustworthy Imams and reliable Huffaz
al-Khatib al-Baghdadi: One of the Huffaz of Hadith and among the great Imams in it
al-Dhahabi: The Hafez and compiler of books
Hajjaj ibn al-Sha'ir al-Baghdadi: I do not know anyone more skilled in this craft than him
Abd al-Rahman ibn Yusuf ibn Khuraysh: He lies deliberately, Ibn Adi said: This is prejudice, and I do not know of any Munkar narration from Abu Mas'ud
Ali ibn al-Madini: He was among those firm in knowledge
Muhammad ibn Ishaq ibn Mandah al-Isbahani: Abu Mas'ud made mistakes in some Hadiths and did not retract them
Yahya ibn Ma'in: I have not seen anyone with a black head who memorizes better than him