[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."
وفي رواية لمسلم: "من اقتنى كلبًا ليس بكلب صيد، ولا ماشية ولا أرض، فإنه ينقص من أجره قيراطان كل يوم".
Reference | : Riyad as-Salihin 1689 |
In-book reference | : Book 17, Hadith 179 |