Abu Dawud said, “The one who relates these reports from al-Jurayri is Ismaʿil ibn ʿUlayyah.”
Abu Jaʿfar Ahmad ibn Saʿid al-Darimi remarked, “No mistake is known of Ibn ʿUlayyah except in Jabir’s hadith about the mudabbar; he switched the slave-boy’s name with the master’s and the master’s name with the boy’s.” (1)
Ahmad ibn Ibrahim al-Dawraqi said, “Some of our companions informed us that Ibn ʿUlayyah had not laughed for twenty years.”
Muhammad ibn al-Muthanna reported, “I spent a night with Ibn ʿUlayyah; he recited one-third of the Quran, and I never saw him laugh at all.”
ʿUbayd Allah al-ʿAyshi said, “The two Hammads narrated to us that Ibn al-Mubarak used to engage in trade and would say, ‘Were it not for five people I would never have traded: the two Sufyans, Fudayl ibn ʿIyad, Ibn al-Sammak, and Ibn ʿUlayyah.’ He would then support them.”
On one of his journeys Ibn al-Mubarak arrived to find that Ibn ʿUlayyah had been appointed judge. He therefore neither visited him nor continued his usual assistance. Ibn ʿUlayyah rode over to see him, but Ibn al-Mubarak did not even raise his head to acknowledge him, so Ibn ʿUlayyah left. The next day he sent ʿAbd Allah a note saying, “I had been waiting for your kindness; I came to you and you did not speak to me. What did you see…"