Musannaf Ibn Abi Shayba 35:210

Sufyan ibn 'Uyaynah narrated to us, from al-Zuhri, from Salim, from his father, who said: The Prophet (may Allah bless him and grant him peace) said: "Whoever acquires a dog, except for a hunting dog or a dog for livestock, a qirat of his reward decreases every day."