It was said to Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him): The Romans take those of our horses that have become exhausted, hasten to use them, and fight on them; shall we hamstring those of our horses that become exhausted? He said: No. They are not able to diminish you in anything; tomorrow they will be your slaves or your dhimmis (protected subjects).
Al-Shafi'i (may Allah have mercy on him) said: It has reached us from Abu Umamah al-Bahili (may Allah be pleased with him) that he advised his son: "Do not hamstring any living body." And from Umar bin Abd al-Aziz (may Allah have mercy on him) that he forbade hamstringing a riding animal when it stops (from exhaustion). And from Qabisah that his horse stopped (from exhaustion) under him in the land of the Romans, so he left it and forbade hamstringing it. Someone who heard Hisham bin al-Ghaz informed us, narrating from Makhul, that he asked him about it and he forbade him, and said: The Prophet (peace and blessings be upon him) "forbade mutilation."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18133