Surah Luqman Verse 19

وَاقْصِدْ فِي مَشْيِكَ وَاغْضُضْ مِنْ صَوْتِكَ ۚ إِنَّ أَنْكَرَ الْأَصْوَاتِ لَصَوْتُ الْحَمِيرِ

And be moderate in your pace and lower your voice; indeed, the most disagreeable of sounds is the voice of donkeys