Musnad Ahmad 28:444

Muhammad ibn Bakr and Abd al-Razzaq narrated to us, they said: Ibn Jurayj informed us, Sulayman al-Ahwal informed me, that Thabit, the freed slave of Umar ibn Abd al-Rahman, informed him: That when there occurred between Abdullah ibn Amr and Anbasah ibn Abi Sufyan what occurred, and they prepared for battle, Khalid ibn al-As rode to Abdullah ibn Amr and admonished him. Abdullah ibn Amr said: "Do you not know that the Messenger of Allah, may Allah bless him and grant him peace, said: 'Whoever is killed defending his property is a martyr'?" And Abd al-Razzaq said: "Whoever is killed over his property is a martyr."