The Book of Funerals
21/47. Chapter:
Concession Allowing One To Not Stand Up
Sunan an-Nasai
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَمَّادٌ، عَنْ أَيُّوبَ، عَنْ مُحَمَّدٍ، أَنَّ جَنَازَةً، مَرَّتْ بِالْحَسَنِ بْنِ عَلِيٍّ وَابْنِ عَبَّاسٍ فَقَامَ الْحَسَنُ وَلَمْ يَقُمِ ابْنُ عَبَّاسٍ فَقَالَ الْحَسَنُ أَلَيْسَ قَدْ قَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم لِجَنَازَةِ يَهُودِيٍّ قَالَ ابْنُ عَبَّاسٍ نَعَمْ ثُمَّ جَلَسَ .
It was narrated from Muhammad that: a funeral passed by Al-Hasan bin 'Ali and Ibn 'Abbas. Al-Hasan stood up but Ibn 'Abbas did not/ Al-Hasan said: 'Didn't the Messenger of Allah stand up for the funeral of a Jew?' Ibn 'Abbas said: 'Yes, then he sat down."'
Reference : Sunan an-Nasa'i 1924In-book reference : Book 21, Hadith 107English translation : Vol. 3, Book 21, Hadith 1925