Sahih Al Bukhari – Book of Agriculture

Volumn 003, Book 039, Hadith Number 515.
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Narated
By Abu Huraira : Allah’s Apostle said, “Whoever keeps a dog, one Qirat
of the reward of his good deeds is deducted daily, unless the dog is
used for guarding a farm or cattle.” Abu Huraira (in another narration)
said from the Prophet, “unless it is used for guarding sheep or farms,
or for hunting.” Narrated Abu Hazim from Abu Huraira: The Prophet said,
“A dog for guarding cattle or for hunting.”