that the Prophet ﷺ said: "Al-'Abbas is the uncle of the Messenger of Allah ﷺ, and indeed, the uncle of a man is the Sinw of his father or from the Sinw of his father."
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ الْعَبَّاسُ عَمُّ رَسُولِ اللَّهِ وَإِنَّ عَمَّ الرَّجُلِ صِنْوُ أَبِيهِ أَوْ مِنْ صِنْوِ أَبِيهِ هَذَا حَدِيثٌ حَسَنٌ غَرِيبٌ لاَ نَعْرِفُهُ مِنْ حَدِيثِ أَبِي الزِّنَادِ إِلاَّ مِنْ هَذَا الْوَجْهِ