Sahih Al Bukhari (175)

حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، قَالَ: حَدَّثَنَا شُعْبَةُ، عَنِ ابْنِ أَبِي السَّفَرِ، عَنِ الشَّعْبِيِّ، عَنْ عَدِيِّ بْنِ حَاتِمٍ، قَالَ: سَأَلْتُ النَّبِيَّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ فَقَالَ: «إِذَا أَرْسَلْتَ كَلْبَكَ المُعَلَّمَ 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»

`Ady ibn Hatim (may Allah be pleased with him) said: I asked the Prophet (peace be upon him) (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."