Musnad Ahmad 834:37

Sa'id ibn 'Amir narrated to us, from Sa'id, from Qatadah, from al-Hasan, from 'Abdullah ibn Mughaffal, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever keeps a dog that is not a hunting dog, nor a dog for crops, nor a dog for livestock, then indeed, one qirat of his reward decreases every day."