The Messenger of Allah ﷺ was present with a she-mule which he rode, so Ali said: If we made asses cover mares we would have animals of this type. The Messenger of Allah ﷺ said: Only those who do not know do that.  

أُهْدِيَتْ لِرَسُولِ اللَّهِ ﷺ بَغْلَةٌ فَرَكِبَهَا فَقَالَ عَلِيٌّ لَوْ حَمَلْنَا الْحَمِيرَ عَلَى الْخَيْلِ فَكَانَتْ لَنَا مِثْلُ هَذِهِ قَالَ رَسُولُ اللَّهِ ﷺ إِنَّمَا يَفْعَلُ ذَلِكَ الَّذِينَ لاَ يَعْلَمُونَ