Abu Dawud said: I asked Ahmad ibn Hanbal (1), “If Israʾil happens to be the sole transmitter of a report, may it be used as evidence?”
He replied, “Israʾil is sound in ḥadith. Yahya used to criticise him over the matter of Abu Yahya al-Qattat; he said that he (Israʾil) had transmitted from him some objectionable narrations (2).”

Ahmad then said, “Yahya ibn Saʿid never narrated anything from him. When Israʾil narrates from his written notebook he omits nothing, and what he transmits can be verified against his book.
In another report Ahmad said, ‘Sharik is more accurate than Israʾil in what he relates from Abu Ishaq.’”

ʿAbbas related from Yahya ibn Maʿin: “Al-Qattan would not transmit from Israʾil, nor from Sharik.”

Ibn Maʿin also said that Yahya ibn Adam remarked, “We used to write while sitting with Israʾil as he recited from memory.”
Yahya added, “At first Israʾil did not have the material memorised; later he committed it to memory”—meaning that he went back and reviewed his notebook.
He further said, “Israʾil is more reliable in his transmission from Abu Ishaq than Shayban.”

Ahmad ibn Zuhayr and others reported from Yahya ibn Maʿin that he said: “Trustworthy.”
Al-ʿIjli said: “Trustworthy.”
Abu Hatim al-Razi said: “Reliable, truthful, and among the most precise of Abu Ishaq’s students.”
Yaʿqub ibn Shaybah said: “Truthful, though not strong,” and on another occasion, “There is some softness in his ḥadith.”

Ahmad ibn Dawud al-Huddani said: I heard ʿIsa ibn Yunus say, “Our companions—Sufyan, Sharik, and others—whenever they disagreed over a ḥadith of Abu Ishaq, they would come to my father, and he would say, ‘Go to my son Israʾil; he has transmitted more from him than I have.’”