Muhammad bin al-Muthanna said: I heard Abd al-Rahman bin Mahdi say that he considered Isra'il reliable in the chain of Abu Ishaq. He said: He used to bring them (the narrations) complete; and whatever I missed of Sufyan's hadith from Abu Ishaq, I missed only because I relied on them through Isra'il.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13616