Chapter 42: The Book of Hunting and Slaughtering
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."
Sunan an-Nasa'i 4280