Musnad Ahmad 27:1092

Muhammad ibn Abd al-Rahman al-Tafawi narrated to us, Ayyub narrated to us, from Nafi’, from Ibn Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The one in the state of ihram may kill five [creatures]: the kite, the crow, the mouse, the scorpion, and the biting dog."