Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "Whoever eats, or drinks, or shoots at game, and then forgets to mention the name of Allah, let him eat of it, as long as he has not deliberately left out the Bismillah."
Al-Tabarani recorded it in al-Mu'jam al-Kabir. Its chain contains a narrator, Utbah bin al-Sakan, and he is matruk (abandoned).
Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "When you mention the name (that is, say Bismillah), then also say Allahu Akbar." The narrator says: That is, do this when slaughtering an animal.
Al-Tabarani recorded it. Its chain contains a narrator, Uthman bin Abd al-Rahman al-Qurashi, and he is da'if (weak).
Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates: A man asked the Prophet (peace and blessings be upon him): What is your view about a man who forgets to say Bismillah while slaughtering an animal? The Prophet (peace and blessings be upon him) said: The name of Allah is on the mouth of every Muslim.
Al-Tabarani recorded it in al-Mu'jam al-Awsat. Its chain contains a narrator, Marwan bin Salim al-Ghifari, and he is matruk (abandoned).