The Messenger of Allah ﷺ said, "Abbas is from me, and I am from him."He said, this is a hasan sahih ghareeb hadith, which we know only through the narration of Israil.
حدثنا القاسم بن دينار الكوفي حدثنا عبيد الله عن إسرائيل عن عبد الأعلى عن سعيد بن جبير
قال رسول الله ﷺ العباس مني وأنا منه قال هذا حديث حسن صحيح غريب لا نعرفه إلا من حديث إسرائيل
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[Its chain of transmission is daif] Nasai narrated it in his Sughra, no. 4779, and his Kubra, no. 8173, from the hadith of Ubaydullah bin Musa with this wording, and Hakim graded it sahih in 3/325, 329, and Dhahabi agreed with him, but Dhahabi contradicted this in Siyar Alam al-Nubala, 2/99, which is the correct position, since Abdul-Ala Thalabi is well-known to be daif.