Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:31:19 –

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

And be modest in your bearing, being moderate in it, neither dragging slowly nor rushing, but peaceful and dignified, and lower your voice; indeed the most hideous of voices is the donkey’s voice’, beginning ˹its hideous bray˺ with an exhalation and ending with an inhalation.
القرآن:٣١:١٩ –

وَاقْصِدْ فِي مَشْيِكَ وَاغْضُضْ مِنْ صَوْتِكَ ۚ إِنَّ أَنْكَرَ الْأَصْوَاتِ لَصَوْتُ الْحَمِيرِ  

{واقصد في مشيك} توسط فيه بين الدبيب والإسراع، وعليك السكينة والوقار {واغضض} اخفض {من صوتك إن أنكر الأصوات} أقبحها {لصوت الحمير} أوله زفير وآخره شهيق.