From Sahih Muslim (Hadith 4021):
Ibn Mughaffal reported:Allah's Messenger (ﷺ) ordered the killing of dogs and then said: what is the trouble with them (the people of Medina)? How dogs are nuisance to them (the citizens of Medina)? He then permitted keehing of dogs for hunting and (the protection of) herds
Reference: Muslim 4021