Musannaf Ibn Abi Shayba 28:206

Sharīk narrated to us, from Ibrāhīm ibn Muhājir, from Ibrāhīm, that Abū Bakr said: "If they were to withhold from me a hobbling rope that they used to give to the Messenger of Allah, may Allah bless him and grant him peace, I would fight them." Then he recited: "And Muhammad is not but a messenger. [Other] messengers have passed on before him," to the end of the verse.