Sunan an-Nasa'i, Hadith 1999 ⓘ
It was narrated from 'Ali bin Abi Talib that: mention was made of standing at the funeral until the body is placed in the grave. 'Ali bin Abi Talib said: "The Messenger of Allah stood, then he sat down."
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ يَحْيَى، عَنْ وَاقِدٍ، عَنْ نَافِعِ بْنِ جُبَيْرٍ، عَنْ مَسْعُودِ بْنِ الْحَكَمِ، عَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ، : أَنَّهُ ذُكِرَ الْقِيَامُ عَلَى الْجَنَازَةِ حَتَّى تُوضَعَ، فَقَالَ عَلِيُّ بْنُ أَبِي طَالِبٍ : قَامَ رَسُولُ اللَّهِ صلى الله عليه وسلم ثُمَّ قَعَدَ .
also referenced under: Book 21, Hadith 183 (In-Book) & Volume 3, Book 21, Hadith 2001 (DarusSalam)