Abu Bakr al-Bayhaqi: Frequently mistaken
Abu Hatim al-Razi: Trustworthy
Abu Zur'ah al-Razi: Trustworthy
Ahmad ibn Hanbal: He was asked about Ayub, Ubayd Allah ibn Umar, and Malik, which of them is more reliable than Nafi'? He said Ubayd Allah is more reliable, more retentive, and narrates more
Ahmad ibn Shu'ayb al-Nasai: Trustworthy and Reliable
Ahmad ibn Salih al-Jili: Trustworthy and Reliable
Ibn Hajar al-Asqalani: Trustworthy and Reliable
Ibn Manjawaih al-Isbahani: He was among the nobles of Quraysh in terms of virtue, knowledge, worship, حفظ, and piety
Al-Dhahabi: Reliable
Ali ibn Umar al-Harbi: Trustworthy, retentive, and agreed upon
Muhammad ibn Sa'd Kathir al-Waqidi: Trustworthy and an authority
Yahya ibn Ma'in: From the trustworthy, and once: an authority, and once: He preferred him in the narration of al-Qasim on the authority of Aisha on the authority of Urwa on her authority, Ubayd Allah is more reliable than Ibn Ajlan