On the authority of ʿĀmir ibn Rabīʿah, conveying it to the Prophet, peace and blessings be upon him: "If you see a funeral procession, stand up for it until it passes you by or is set down."(1)

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(1) Its chain of transmission is authentic. Sālim: he is Ibn ʿAbd Allāh ibn ʿUmar ibn al-Khaṭṭāb, and Sufyān: he is Ibn ʿUyaynah, and Musaddad: he is Ibn Musarhad.
It was also recorded by al-Bukhārī (1307), Muslim (958), Ibn Mājah (1542), al-Tirmidhī (1563), and al-Nasāʾī (1916) via Ibn Shihāb al-Zuhrī, with this chain of transmission.
It was also recorded by al-Bukhārī (1308), Muslim (958), and al-Nasāʾī (1915) via Nāfiʿ, the freed slave of Ibn ʿUmar, from Ibn ʿUmar, with it.
It is also in the Musnad of Aḥmad (15687), and the Ṣaḥīḥ of Ibn Ḥibbān (3051).
Ibn al-Mundhir said: The people of knowledge have differed regarding standing up for funeral processions when they pass by. One group said: one stands up for it, and this was done by Abū Masʿūd al-Badrī, Abū Saʿīd al-Khudrī, Qays ibn Saʿd, Sahl ibn Ḥunayf, and Sālim ibn ʿAbd Allāh.
Another group held that a person should not stand up for a funeral procession passing by him. A funeral procession passed by Saʿīd ibn al-Musayyab and he did not stand up for it, and ʿUrwah ibn al-Zubayr used to disapprove of those who did that. Mālik said: A man is not obliged to stand up for a funeral procession when he sees it, nor to sit until it passes him by, whether the deceased was a Muslim or an unbeliever. Al-Shāfiʿī said: One who does not attend the funeral does not stand up for it, and standing up for it is abrogated. Aḥmad said: If he stands up, he does not sit down, and if he sits, there is no harm in it. Isḥāq said the same.
Aḥmad said: His statement, "Let him stand up," applies only to one who is sitting; he stands up.
Aḥmad said: Whoever stands up for a funeral procession, that is fine, and whoever does not stand up follows the ḥadīth of ʿAlī [which is what Mālik recorded in al-Muwaṭṭaʾ 1/232, al-Shāfiʿī in al-Umm 1/279, and Muslim (962), and it will come later in this work under number (3175): that the Messenger of Allah, peace and blessings be upon him, stood up for a funeral procession, then sat down. In one wording of Muslim: We saw the Messenger of Allah, peace and blessings be upon him, stand up, so we stood up, and he sat down, so we sat down, [meaning regarding the funeral]. Abū ʿAbd Allāh [meaning Aḥmad] said: As for me, I do not stand up. The Messenger of Allah, peace and blessings be upon him, stood up, so we stood up, and he sat down, so we sat down. Then Ibn al-Mundhir said: The view of Aḥmad and Isḥāq is good in both respects.
We say: Among those who also held that this report is abrogated by the ḥadīth of ʿAlī coming later in this work under number (3175) are al-Ṭaḥāwī in Sharḥ Maʿānī al-Āthār 1/488, and al-Ḥāzimī in al-Iʿtibār, p. 129, and before them al-Ḥumaydī, the teacher of al-Bukhārī, as in al-Tamhīd 23/262.