Musnad Ahmad 27:290

Ibn Numayr narrated to us, Hajjaj informed us, from Wabarah, from Ibn Umar, who said: "The Messenger of Allah, may Allah bless him and grant him peace, commanded the killing of the mouse, the crow, and the wolf." It was said to Ibn Umar: "And the snake and the scorpion?" He said: "That used to be said as well."