I heard the Messenger of Allah ﷺ say to the two messengers, after they had read the letter of Musaylima the Liar, "What do the two of you say?"They replied, "We say what he says."The Messenger of Allah ﷺ said, "By Allah, were it not that messengers are not to be killed, I would have struck off both your heads."
سمعت رسول الله ﷺ يقول للرسولين حين قرأ كتاب مسيلمة الكذاب: فما تقولان أنتما؟ قالا: نقول كما قال. فقال رسول الله ﷺ: أما والله لولا أن الرسل لا تقتل لضربت أعناقكما.
Abu Dawud (2761), Ahmad (15989), Tirmidhi in Ilal al-Kabir (2/953), and Hakim (3/52-53 and 2/142-143) all narrated this through the chain of Muhammad bin Ishaq, who said, "Saad bin Tariq Ashjai narrated to me, from Salama bin Naim bin Masud Ashjai, from his father," and he related the account. Its chain of transmission is hasan because of Muhammad bin Ishaq, for his hadith is hasan when he states his source explicitly.Tirmidhi said, "I asked Muhammad about this hadith, and he said, 'Ibn Abu Zaida also narrated it from Saad bin Tariq, and he considered it a hasan hadith.'" Hakim said, "Sahih according to the criteria of Muslim."Ibn Ishaq also mentioned that Musaylima wrote a letter to the Messenger of Allah ﷺ, which he sent with two messengers, and its text was as follows, "From Musaylima, messenger of Allah, to Muhammad, messenger of Allah, peace be upon you. To proceed, I have been made a partner with you in this matter. Half the earth belongs to us and half to Quraysh, but Quraysh are a people who transgress." His two messengers then came to him bearing this letter.Ibn Ishaq said, "An elder from Ashja narrated to me, from Salama bin Naim bin Masud Ashjai, from his father Naim, who said, 'I heard the Messenger of Allah ﷺ say to the two of them, once he had read the letter, "What do you two say?" They said, "We say what he said." He said, "By Allah, were it not that messengers are not killed, I would strike off your heads."'"Then he wrote to Musaylima, "In the name of Allah, the Most Gracious, the Most Merciful. From Muhammad, messenger of Allah, to Musaylima the liar, peace be upon those who follow guidance. To proceed, "the earth belongs to Allah. He gives it as an inheritance to whomever He wills of His servants, and the ultimate outcome is for the righteous" [Araf 7:128]." That was at the end of the tenth year. Ibn Hisham mentioned it in his Sira (2/600-601).As for Bukhari's inclusion of the story of Thumama bin Athal in the hadith of Abu Hurairah (4372) within the account of the delegation of Banu Hanifa, there is an error in that. He was not part of the delegation of Banu Hanifa, and had he been part of the delegation, he would not have been brought in bonds, nor tied to a pillar of the masjid. Rather, he had accepted Islam in the sixth year, before the delegation of Banu Hanifa that came to Madinah after the Conquest and before the tenth year. His acceptance of Islam has already been mentioned in connection with the expedition of Muhammad bin Maslama toward Najd in the sixth year.Hafiz Bayhaqi got it right, mentioning his story in the account of the expedition to Najd, in Dalail (4/78), which took place in the sixth year, and he included in it the hadith of Abu Hurairah referred to above, without mentioning Thumama bin Athal in connection with the delegation of Banu Hanifa. Dalail (5/330).As for his coming as a messenger for Musaylima to the Messenger of Allah ﷺ, this has been narrated in a daif hadith from Abdullah bin Masud, who said, "Ibn Fawaha and Ibn Athal came as two messengers for Musaylima to the Messenger of Allah ﷺ, and the Messenger of Allah ﷺ said to them, 'Do you two testify that I am the messenger of Allah?' They said, 'We testify that Musaylima is the messenger of Allah.' The Messenger of Allah ﷺ said, 'I believe in Allah and His messengers. Had I been one who kills messengers, I would have killed you both.'"Abu Dawud Tayalisi narrated it (248), saying, "Masudi narrated to us, from Asim, from Abu Waail, from Abdullah bin Masud," and he related it. Masudi's memory became confused, and Abu Dawud Tayalisi narrated from him after this confusion had set in. Imam Ahmad also narrated it (3708) from Yazid, who said Masudi informed us, with his chain of transmission, and Yazid bin Harun is likewise among those who narrated from Masudi after his confusion had set in. Masudi also used to make errors in what he narrated from Asim, who is Ibn Abu Najud.This hadith has come through other established chains of transmission that do not mention Thumama, and it is documented in the book on jihad.