Sahih Muslim Book 7, Hadith Number 2708.

Chapter : Hunting is forbidden for one who is in the state of Ihram.

Abu Qatada (Allah be pleased with him) reported that while he was with the Messenger of Allah (may peace be upon him) on one of the highways of Mecca, he lagged behind him (the Holy Prophet) along with companions who were in the state of Ihram, whereas he was himself not Muhrim. He saw a wild ass. As he was mounting his horse he asked his companions to pick up for him his whip (which had dropped) but they refused to do so. He asked them to hand him over the spear, but they refused. He then himself took hold of it and chased the wild ass and killed it. Some of the Companions of the Apostle of Allah (way peace be upon him) ate (its meat), but some of them refused to do so. They overtook the Messenger of Allah (may peace be upon him) and asked him about it, and he said: It is a food which Allah provided you (so eat it).