It is narrated from Sayyiduna Imran bin Husayn (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) forbade mutilation, and he would say: "Mutilation is for a man to swear that he will perform Hajj on foot. Whoever swears any such oath, let him expiate his oath and then ride."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15434