Musnad Ahmad 28:347

Waki’ narrated to us, from Sufyan, from ‘Abdullah ibn Hasan, from his maternal uncle Ibrahim ibn Muhammad ibn Talhah, from ‘Abdullah ibn ‘Amr, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever has his wealth sought [to be taken] without right, and he is killed defending it, then he is a martyr."