Musnad Ahmad 30:3024

Waki' narrated to us, he said: Ali ibn al-Mubarak and Isma'il narrated to us, they said: Ali ibn al-Mubarak informed us, from Yahya ibn Abi Kathir, from Damdam ibn Jaws al-Haffani, from Abu Hurayrah, he said: "The Messenger of Allah, may Allah bless him and grant him peace, commanded us to kill the two black ones during prayer: the scorpion and the snake."