Sunan an-Nasa'i 1917
سنن النسائي#1917SahihIt was narrated that Abu Sa'eed said:"The Messenger of Allah said: 'When you see a funeral, stand up, and whoever follows it, let him not sit down until (the body) is placed (in the grave)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiHasan
In-book reference: 21:100