It was narrated form 'Amir bin Rabi'ah Al-'Adawi that the Messenger of Allah said:"When you see a funeral, stand up until it has passed you, or (the body) is placed (in the grave)
Hadith No. 1916
Sunan an Nasai
Gradings:
Abu Ghuddah:
Sahih
Al-Albani:
Sahih
Zubair Ali Zai:
Sahih - Agreed Upon