When he saw a funeral, he would stand until it had passed

Salim bin Abdullah narrates from his father, Sayyiduna Abdullah bin Umar (may Allah be pleased with them both), that whenever a funeral passed by the Messenger of Allah (peace and blessings be upon him), he would stand until it had passed.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it. This is not the text of the hadith of Sayyiduna Ibn Umar from Amir bin Rabi'ah, for that text concerns accompanying the funeral, while this one concerns standing for the funeral, despite the many differences among the narrations on this matter.

Al-Ala' bin Abd al-Rahman narrates from his father that he attended a funeral whose prayer was led by Marwan bin al-Hakam. Then Sayyiduna Abu Hurayrah (may Allah be pleased with him) went with Marwan to the graveyard and the two of them sat down there. Meanwhile Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) came and said to Marwan: "Give me your hand." Marwan gave him his hand, and he said: "Stand up." So Marwan stood up. Then Marwan asked: "Why did you make me stand?" He replied: "Whenever the Messenger of Allah (peace and blessings be upon him) saw a funeral, he would stand until it had passed, and he would say: 'Death is indeed something frightening (and terrifying).'" Marwan asked: "O Abu Hurayrah, is this true?" He said: "Yes." Marwan said: "Then what prevented you from telling me?" He replied: "You were the imam (the governor); when you sat down, I sat down too."
This hadith is sahih (authentic) on the condition of Muslim, but they did not record it with this wording.

It is narrated from Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) that a man asked the Messenger of Allah (peace and blessings be upon him): "O Messenger of Allah, the funeral of a disbeliever passes by us; should we stand for it?" He said: "Yes, stand for it, for you are not standing for it (the deceased); rather, you stand out of reverence and glorification for the One who takes the souls."
The chain of this hadith is sahih (authentic), but the two Shaykhs did not record it.

It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that the funeral of a Jew passed by the Messenger of Allah (peace and blessings be upon him) and he stood up. The people said: "O Messenger of Allah, this is the funeral of a Jew." He said: "I stood only because of the angels."
This hadith is sahih (authentic) on the condition of Muslim, but the two Shaykhs did not record it with this wording; however, the two of them agreed on recording the hadith of Ubaydullah bin Miqsam from Sayyiduna Jabir (may Allah be pleased with him) about standing for the funeral of a Jew.

Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) narrates: When the Prophet (peace and blessings be upon him) came (to Madinah), our practice was that when death approached one of us, we would inform him. He would come and seek forgiveness for him, until, when he passed away, he and his companions would return; and sometimes he had to remain there until the burial, which took a long time. When we felt that this caused hardship for the Prophet (peace and blessings be upon him), we said to one another that we should not inform him until someone's soul had been taken, and inform him once the soul had been taken, so that he would not be troubled with hardship and waiting. So after that, we would inform him after someone had died, and he would come and lead the funeral prayer over him.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.

Sa'id bin Abi Sa'id narrates that Sayyiduna Ibn Abbas (may Allah be pleased with them both) led a funeral prayer and recited "Al-hamdu lillah" (Surah al-Fatihah) aloud. Then he said: "I recited it aloud only so that you would know that it is a Sunnah."
This hadith is sahih (authentic) on the condition of Muslim, and all agree that a Companion's saying "it is a Sunnah" carries the ruling of a musnad (Prophetic) hadith. It also has a supporting narration (shahid) with an authentic chain which Bukhari recorded: