Sahih Muslim 962 d
It is narrated on the authority of Muhammad b. Munkadir that he said:
I heard from Mas'ud b. al-Hakam who narrated it on the authority of Hadrat 'Ali that he said: We saw the Prophet (ﷺ) stood up for a (bier) and we also stood up; he sat down and we too sat down.
وَحَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ، حَدَّثَنَا شُعْبَةُ، عَنْ مُحَمَّدِ، بْنِ الْمُنْكَدِرِ قَالَ سَمِعْتُ مَسْعُودَ بْنَ الْحَكَمِ، يُحَدِّثُ عَنْ عَلِيٍّ، قَالَ رَأَيْنَا رَسُولَ اللَّهِ صلى الله عليه وسلم قَامَ فَقُمْنَا وَقَعَدَ فَقَعَدْنَا ‏.‏ يَعْنِي فِي الْجَنَازَةِ ‏.‏