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Muhammad b. Sinn said that when a bier came past al-Hasan b. ‘All and Ibn ‘Abbas al-Hasan stood up but Ibn ‘Abbas did not, so al- Hasan said, “Did God’s messenger not stand up out of respect for the bier of a Jew ?” He replied, “Yes, but thereafter he sat.” Nasa’i transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ مُحَمَّدِ بْنِ سِيرِينَ قَالَ: إِنَّ جَنَازَةً مَرَّتْ بِالْحَسَنِ بْنِ عَلِيٍّ وَابْنِ عَبَّاسٍ فَقَامَ الْحَسَنُ وَلَمْ يَقُمِ ابْنُ عَبَّاسٍ فَقَالَ الْحَسَنُ: أَلَيْسَ قَدْ قَامَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لِجَنَازَةِ يَهُودِيٍّ؟ قَالَ: نَعَمْ ثُمَّ جلس. رَوَاهُ النَّسَائِيّ
sunnah.com