Abu Dawud Book 8, Hadith Number 2661.

Narated By Samurah ibn Jundub : Al-Hayyaj ibn Imran ibn Husayn reported that a slave of Imran ran away. He took a vow to Allah that if he overpowers him, he will cut off his head. He then sent me (to Samurah ibn Jundub) to ask him about this question for him. I came to Samurah ibn Jundub and asked him. He said: The Apostle of Allah (PBUH) used to exhort us to give alms (sadaqah) and forbid us to mutilate (a slain). I then came to Imran ibn Husayn and asked him. He said: The Apostle of Allah (PBUH) used to exhort us to give alms (sadaqah) and forbid us to mutilate (a slain).