Sahih Muslim Book 10, Hadith Number 3818.
Chapter : Riba (Usury).
Salim b. ‘Abdullah reported on the authority of his father that Allah’s Messenger (may peace be upon him) said: He who kept a dog other than one meant for watching the herd or for hunting would lose every day two qirat of his good deeds. ‘Abdullah and Abu Huraira also said: Or dog meant for watching the field.