Imam al-Shafi'i (may Allah have mercy on him) says: Isma' is game which the dogs kill while you are watching, and inma' is game which dies out of your sight. Imam al-Shafi'i (may Allah have mercy on him) says: In my view nothing is permissible in this except this, unless something has been narrated about it from the Prophet (peace and blessings be upon him), which I suspect there has; then everything that contradicts the command of the Prophet (peace and blessings be upon him) falls away, and neither opinion nor analogy is equal to it, for Allah Almighty has cut off every excuse through his (peace and blessings be upon him) word.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيد والذبائح / 18903