Musnad Ahmad 28:74

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from 'Amr ibn Dinar, from Suhayb, the freed slave of Ibn 'Amir, who narrates from 'Abdullah ibn 'Amr, that the Prophet (peace and blessings of Allah be upon him) said: "Whoever slaughters a sparrow or kills it for no reason—'Amr said: I think he said:—except for its right, Allah will ask him about it on the Day of Resurrection."