Sunan an-Nasa'i 4286
It was narrated that Ibn 'Umar said:
"The Messenger of Allah said:' whoever keeps a dog except one that is trained for hunting or a dog for herding livestock, two 
Qirats will be deducted from his reward each day."
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّهُ سَمِعَهُ يَقُولُ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏
"‏ مَنْ أَمْسَكَ كَلْبًا إِلاَّ كَلْبًا ضَارِيًا أَوْ كَلْبَ مَاشِيَةٍ نَقَصَ مِنْ أَجْرِهِ كُلَّ يَوْمٍ قِيرَاطَانِ ‏"‏ ‏.‏