Sahih Muslim Book 032, Hadith Number 6249.
Hadith Section/Book: Sahih Muslim Sahih Muslim Book 32. Virtues, Good Manners and Joining Of The Ties Of Relationship
Chapter : It is forbidden to commit oppression.
Ibu 'Umar reported Allah's Messenger (may peace be upon him) as saying: Oppression is the darkness on the Day of Resurrection.