عَنْ أَبِي مَعْمَرٍ قَالَ: كُنَّا مَعَ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ فَمَرَّ بِهِ جَنَازَةٌ فَقَامَ لَهَا نَاسٌ فَقَالَ عَلِيٌّ رَضِيَ اللَّهُ عَنْهُ: مَنْ أَفْتَاكُمْ هَذَا؟ فَقَالُوا: أَبُو مَوسَى، فَقَالَ: إِنَّمَا فَعَلَ ذَلِكَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ مَرَّةً فَكَانَ يَتَشَبَّهُ بِأَهْلِ الْكِتَابِ، فَلَمَّا نُهِيَ انْتَهَى
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.