Musnad Abu Ya'la al-Mawsili 111:131

Narrated to us Zuhayr, narrated to us ‘Abd al-Malik ibn ‘Amr, narrated to us Zuhayr ibn Muhammad, from ‘Amr ibn Abi ‘Amr, from ‘Ikrimah, from Ibn ‘Abbas, from the Prophet (may Allah bless him and grant him peace), who said: "Whoever you find committing an act with an animal, kill him and kill the animal with him. And whoever you find doing the deed of the people of Lot, kill the doer and the one to whom it is done."