Riyad as-Salihin 1689
Abu Hurairah (May Allah be pleased with him) said:
The Messenger of Allah (ﷺ) said, "He who keeps a dog, will lose out of his good deeds equal to one Qirat every day, except one who keeps it for guarding the fields or the herd." [Al-Bukhari and Muslim] . In a narration of Muslim, the Messenger of Allah (ﷺ) is reported to have said: "He who keeps a dog for any reason other than to guard his property (lands) or his flock of sheep, his good deeds equal to two Qirat will be deducted every day."
وعن أبي هريرة رضي الله عنه قال‏:‏ قال رسول الله صلى الله عليه وسلم ‏:‏ ‏"‏من أمسك كلبًا فإنه ينقص كل يوم من عمله قيراط إلا كلب حرث أو ماشية‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏‏.‏  
وفي رواية لمسلم‏:‏ ‏"‏من اقتنى كلبًا ليس بكلب صيد، ولا ماشية ولا أرض، فإنه ينقص من أجره قيراطان كل يوم‏"‏‏.‏