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.