The prohibition of fighting one who says La ilaha illa Allah

It is narrated from Sayyiduna Ayman bin Khuraym (may Allah be pleased with him) that Marwan bin al-Hakam said to him: Will you not come out and fight alongside us? He replied: My father and my paternal uncle both took part in the Battle of Badr, and they both instructed me not to fight anyone who says 'La ilaha illallah' (there is no god but Allah). If you bring me a release from the Fire (a guarantee of salvation), I will fight alongside you. Marwan said: Then leave us. So he went out reciting these verses: "I am not one to kill a man who prays / merely for the sake of the rule of another king of Quraysh / who has his own power, while the sin falls upon me / I seek refuge in Allah from ignorance and rashness. / Shall I kill a Muslim without any crime? / If I did so, my life would bring me no benefit as long as I live."
This hadith has a sahih (authentic) chain of narration on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it. And because of the two Companions mentioned, who took part in Badr, this hadith falls within the scope of the musnad (connected) reports.

It is narrated from Abu Thawr al-Huddani that Sayyiduna Uthman bin Affan (may Allah be pleased with him) sent Sa'id bin al-As to Kufah on Yawm al-Jara'ah (the day of al-Jara'ah). The people went out to him and turned him back. The narrator said: I was sitting with Sayyiduna Abu Mas'ud and Sayyiduna Hudhayfah (may Allah be pleased with them both), and Abu Mas'ud said: I did not think that these people would turn back in such a way that not even a cupping-vessel's worth of blood would be shed. And I had no knowledge about this trial except what I learned while Muhammad (peace and blessings be upon him) was alive: "that a man will be a believer in the morning and by evening will have nothing (of faith) with him, and will be a believer in the evening and by morning will have nothing; he will fight in the trial today and tomorrow Allah will destroy him; his heart will be turned upside down and his backside will be raised above him (that is, he will be disgraced and humiliated)." I asked: His lower part? He said: Yes, his backside (that is, he will be turned completely upside down).
This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.

Alqamah bin Abi Alqamah narrates from his mother that a man named "Baba" had a slave. Baba used to beat him and punish him for various things, and the slave bore enmity toward his master, so he sold him. One day the slave met him, and he had a sword with him; this was during the governorship of Sa'id bin al-As. The slave drew his sword on Baba and tried to attack him, but the people held him back. Then Baba came to Sayyidah Aishah (may Allah be pleased with her) and told her what the slave had done. Sayyidah Aishah (may Allah be pleased with her) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever points a piece of iron (a weapon) at any of the Muslims intending to kill him, his blood has become lawful." Sayyidah Aishah (may Allah be pleased with her) said: Baba left her and went to the slave's new master who had bought him, and asked him to cancel the sale. He cancelled the sale and returned the slave to him, and Baba took him and killed him.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.