It was narrated from 'Abdullah bin Mughaffal that the Messenger of Allah said:"Were it not that dogs form one of the communities (or nations - of creatures), I would have commanded that they be killed. But kill those that are all black. Any people who keep a dog, except for dogs used for farming, hunting or herding livestock, one Qirat will be deducted from their reward each day

English translation · Sunan an-Nasa'i