Eating the property of people unjustly is one of the great sin
Imam Ali (AS):
It is a great transgression if somebody possesses someone`s property, while he has no right to it.
اَعظَمُ الخَطَایَا اقتِطَاعُ مَالِ امرِیءٍ مُسلِمٍ بِغَیرِ حَقٍّ.
Al-Wasail, Vol. 16, p. 46