Sahih Muslim Book 7, Hadith Number 2707.

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

Abu Qatada reported: We went with the Messenger of Allah (may peace be upon him) till we reached al-Qaha (a place three stages away from Medina). Some of us were in the state of Ihram and some of us were not. I saw my companions looking towards something, and as I saw I found It to be a wild ass. I saddled my horse and took up my spear and then mounted upon (the horse) and my whip, fell down. I said to my companions as they were in the state of Ihram to pick up the whip for me but they said: By Allah, we cannot help you in any (such) thing (i.e. hunting). So I dismounted (the horse) and picked it (whip) up and mounted again and caught the wild ass after chasing it. It was behind a hillock and I attacked it with my spear and killed it. Then I brought it to my companions. Some of them said: Eat it, while others said: Do not eat it. The Apostle of Allah (may peace be upon him) was in front of us. I moved my horse and came to him (and asked him), whereupon he said: It is permissible, so eat it.