Sahih Muslim Book 4, Hadith Number 2100.

Chapter : Abrogation of the act of standing up the bier.

Mas’ud b. al-Hakam al-Ansari informed Nafi’ that he had heard Hadrat ‘Ali (may Allah be pleased with him), son of Abu Talib, say about the biers: Verily, the Holy Prophet (may peace be upon him) used to stand first but later on kept sitting; but it is also narrated that Nafi’ Ibn Jubair saw Waqid b. ‘Amr standing for a bier till it was placed down.