Surah Luqman — Ayah 19 (31:19)
وَٱقۡصِدۡ فِي مَشۡيِكَ وَٱغۡضُضۡ مِن صَوۡتِكَۚ إِنَّ أَنكَرَ ٱلۡأَصۡوَٰتِ لَصَوۡتُ ٱلۡحَمِيرِ ١٩
English translation (Saheeh International)
And be moderate in your pace and lower your voice; indeed, the most disagreeable of sounds is the voice of donkeys."
Brief commentary
Be moderate in your manner of walking: between hastiness and lethargy, displaying dignity. And lower your voice; do not raise it such that it causes inconvenience. Indeed, the most hideous of sounds is that of the donkey because of them being loud.