Sunan an-Nasa'i, Book 42, Hadith 24 (In-Book) ⓘ
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 " .
also referenced under: Hadith 4286 (Reference) & Volume 5, Book 42, Hadith 4291 (DarusSalam)