The Prophet (ﷺ) said, "When you see a funeral procession, you should stand up, and whoever accompanies it should not sit till the coffin is put down."
Sahih al-Bukhari Book 23, Hadith 68
← Previous Hadith That his father said, "While we were accompanying a funeral procession, Abu Huraira got hold of the hand of Marwan and they sat down before the coffin was put down. Then Abu Sa`id came and took hold of Marwan's hand and said, "Get up. By Allah, no doubt this (i.e. Abu Huraira) knows that the Prophet forbade us to do that." Abu Huraira said, "He (Abu Sa`id) has spoken the truth."

Sahih al-Bukhari Book 23, Hadith 67 Next Hadith → A funeral procession passed in front of us and the Prophet (ﷺ) stood up and we too stood up. We said, 'O Allah's Messenger (ﷺ)! This is the funeral procession of a Jew." He said, "Whenever you see a funeral procession, you should stand up."

Sahih al-Bukhari Book 23, Hadith 69