Sunan an-Nasa'i 4092
It was narrated from Sulaiman bin Buraidah that his father said:
"The Messenger of Allah [SAW] said: 'Whoever is killed defending his wealth, he is a martyr.'"
أَخْبَرَنَا أَحْمَدُ بْنُ نَصْرٍ، قَالَ حَدَّثَنَا الْمُؤَمَّلُ، عَنْ سُفْيَانَ، عَنْ عَلْقَمَةَ بْنِ مَرْثَدٍ، عَنْ سُلَيْمَانَ بْنِ بُرَيْدَةَ، عَنْ أَبِيهِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏
"‏ مَنْ قُتِلَ دُونَ مَالِهِ فَهُوَ شَهِيدٌ ‏"‏ ‏.‏