Abu Muammar says: We were sitting with Sayyiduna Ali (may Allah be pleased with him) when a funeral procession passed by, and the people stood up upon seeing it. Sayyiduna Ali (may Allah be pleased with him) asked: Who gave you the fatwa to stand up? The people said that Sayyiduna Abu Musa (may Allah be pleased with him) did. Upon hearing this, Sayyiduna Ali (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) did this act only once, and the reason was that he (peace and blessings be upon him) liked to adopt conformity with the People of the Book. But when (from Allah) he (peace and blessings be upon him) was forbidden, he (peace and blessings be upon him) stopped.
Hadith Referenceالفتح الربانی / أبواب صلاة الجنازة / 3232
Benefits: … The statement of Sayyiduna Ali radi Allahu anhu that the Prophet sallallahu alayhi wa sallam did this only with a single Jew—our submission is that Sayyiduna Ali radi Allahu anhu was aware of only one incident, otherwise, from the ahadith of the previous chapter, it is evident that this incident occurred more than once.
Benefits: … The statement of Sayyiduna Ali radi Allahu anhu that the Prophet sallallahu alayhi wa sallam did this only with a single Jew—our submission is that Sayyiduna Ali radi Allahu anhu was aware of only one incident, otherwise, from the ahadith of the previous chapter, it is evident that this incident occurred more than once.