BELIEVE in God and His Apostle, and spend on others out of that of which He has made you trustees: or, those of you who have attained to faith and who spend freely [in God’s cause] shall have a great reward.
Al-Hadid (Iron) Verse 7
I heard the Prophet saying, "Whoever is killed while protecting his property then he is a martyr."
Sahih Bukhari: Volume 3, Book 43, Number 660