Sahih Bukhari Volume 1, Book 4, Hadith 175

حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنِ ابْنِ أَبِي السَّفَرِ، عَنِ الشَّعْبِيِّ، عَنْ عَدِيِّ بْنِ حَاتِمٍ، قَالَ سَأَلْتُ النَّبِيَّ صلى الله عليه وسلم فَقَالَ ‏"‏ إِذَا أَرْسَلْتَ كَلْبَكَ الْمُعَلَّمَ فَقَتَلَ فَكُلْ، وَإِذَا أَكَلَ فَلاَ تَأْكُلْ، فَإِنَّمَا أَمْسَكَهُ عَلَى نَفْسِهِ ‏"‏‏.‏ قُلْتُ أُرْسِلُ كَلْبِي فَأَجِدُ مَعَهُ كَلْبًا آخَرَ قَالَ ‏"‏ فَلاَ تَأْكُلْ، فَإِنَّمَا سَمَّيْتَ عَلَى كَلْبِكَ، وَلَمْ تُسَمِّ عَلَى كَلْبٍ آخَرَ ‏"

Narrated By 'Adi bin Hatim : I asked the Prophet (about the hunting dogs) and he replied, "If you let loose (with Allah's name) your tamed dog after a game and it hunts it, you may eat it, but if the dog eats of (that game) then do not eat it because the dog has hunted it for itself." I further said, "Sometimes I send my dog for hunting and find another dog with it. He said, "Do not eat the game for you have mentioned Allah's name only on sending your dog and not the other dog."