Musnad Ahmad 785:17

'Abd al-Wahid al-Haddad Abu 'Ubaydah narrated to us, from Khalaf—meaning Ibn Mihran—, 'Amir al-Ahwal narrated to us, from Salih ibn Dinar, from 'Amr ibn al-Sharid, who said: I heard al-Sharid saying: I heard the Messenger of Allah, may Allah bless him and grant him peace, saying: "Whoever kills a sparrow in vain, it will cry out to Allah, the Almighty and Majestic, on the Day of Resurrection because of him, saying: 'O Lord, such-and-such person killed me in vain, and he did not kill me for any benefit.'"