Sahih Muslim Book - 1, Hadith - 533

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ حَدَّثَنَا وَكِيعٌ ح و حَدَّثَنَا أَبُو كُرَيْبٍ حَدَّثَنَا أَبُو مُعَاوِيَةَ كِلَاهُمَا عَنْ الْأَعْمَشِ بِهَذَا الْإِسْنَادِ غَيْرَ أَنَّهُمَا قَالَا مَا أَنْتُمْ يَوْمَئِذٍ فِي النَّاسِ إِلَّا كَالشَّعْرَةِ الْبَيْضَاءِ فِي الثَّوْرِ الْأَسْوَدِ أَوْ كَالشَّعْرَةِ السَّوْدَاءِ فِي الثَّوْرِ الْأَبْيَضِ وَلَمْ يَذْكُرَا أَوْ كَالرَّقْمَةِ فِي ذِرَاعِ الْحِمَارِ.

It was narrated from Al-A'mash with this chain (a similar Hadith as no. 532), except that they said: "On that Day you will be among the people like a white hair on a black bull or like a black hair on a white bull," and they did not mention: "Like the mark on the foreleg of a donkey."