I heard Messenger of Allah (ﷺ) as saying: He who kept a dog (other than that) which is indispensable for watching the field or the animals would lose one qirat out of his deeds every day. As-Sa'ib b Yazid (one of the narrators) said: Did you hear it from Allah's Messenger (ﷺ)? He said: Yes. by the Lord of this mosque.
Sahih Muslim Book 22, Hadith 75