Sahih Muslim 962 a
It is narrated on the authority of Waqid:
Nafi' b. Jubair saw me and we were standing for a bier, while he was sitting and waiting for the bier to be placed on the ground. He said to me: What makes you keep standing? I said: I am waiting that the bier may be placed on the ground (and I am doing that) on the hadith narrated to me by Abu Sa'id al-Khudri. Upon this Nafi' said: Verily, Mas'ud b. Hakam reported to me on the authority of Hadrat 'Ali b. Abu Talib that the Prophet (ﷺ) stood up first (for a bier) and then sat down.
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، ح وَحَدَّثَنَا مُحَمَّدُ بْنُ رُمْحِ بْنِ الْمُهَاجِرِ، - وَاللَّفْظُ لَهُ - حَدَّثَنَا اللَّيْثُ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنْ وَاقِدِ بْنِ عَمْرِو بْنِ سَعْدِ بْنِ مُعَاذٍ، أَنَّهُ قَالَ رَآنِي نَافِعُ بْنُ جُبَيْرٍ وَنَحْنُ فِي جَنَازَةٍ قَائِمًا وَقَدْ جَلَسَ يَنْتَظِرُ أَنْ تُوضَعَ الْجَنَازَةُ فَقَالَ لِي مَا يُقِيمُكَ فَقُلْتُ أَنْتَظِرُ أَنْ تُوضَعَ الْجَنَازَةُ لِمَا يُحَدِّثُ أَبُو سَعِيدٍ الْخُدْرِيُّ ‏.‏ فَقَالَ نَافِعٌ فَإِنَّ مَسْعُودَ بْنَ الْحَكَمِ حَدَّثَنِي عَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ أَنَّهُ قَالَ قَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم ثُمَّ قَعَدَ ‏.‏