Malik related to me from al-Ala ibn Abd ar-Rahman from Mabad ibnKab as-Salami from his brother Abdullah ibn Kab ibn Malik al-Ansarifrom Abu Umama that the Messenger of Allah, may Allah bless him andgrant him peace, said, "Whoever cuts off the right of a muslim man byhis oath, Allah forbids him the Garden and obliges the Fire for him."They said, "Even if it is something insignificant, Messenger ofAllah?" He said, "Even if it is a tooth-stick, even if it is a tooth-stick," repeating it three times.
USC-MSA web (English) reference: Book 36, Hadith 11
Arabic reference: Book 36, Hadith 1415