While giving da'wah to a leader of Banu Amir ibn Sa'sa'ah, the Prophet ﷺ offered to show him a miracle. At his invitation, the chieftain called out to a small date palm in a nearby grove to come to him, and the sahabi narrating the account says the tree crawled all the way until it stood before him. The Prophet ﷺ then told it to go back, and it returned to its place. The chieftain accepted Islam on the spot.
Around 4 AH, a chieftain of Najd (the highlands of north-central Arabia) named Abu Bara Amir ibn Malik stayed in Madinah for a while. He did not accept Islam, but he was impressed by it. He asked the Prophet ﷺ to send Companions to call the people of Najd to Islam, and he promised them his protection. The Prophet ﷺ chose 70 of the best reciters of the Qur'an and preachers. Most of them were Ahl al-Suffa, the poor Companions who lived at the Prophet ﷺ's mosque and devoted themselves to worship and learning. When the 70 reached the Well of Bir Ma'una, they sent Haram ibn Milhan with a letter to Amir ibn al-Tufayl, the arrogant chieftain of a local tribe. Amir signalled to one of his men, who speared Haram from behind. Killing a messenger who also had protection was a grave betrayal. Amir then called on the tribes to help him kill the rest. Many refused because of Abu Bara's protection. But three clans, Asiya, Ra'l and Dhakwan, agreed. About 400 to 500 men surrounded the Companions, who had not come prepared for battle, and killed them. Three men were not killed in that attack. Ka'b ibn Zayd was wounded and lay unconscious under the bodies of the martyrs, so the attackers did not see that he was alive. Amr ibn Umayyah and al-Mundhir ibn Muhammad had been away from the camp on an errand. When they returned, they saw vultures circling. Amr wanted to go back and tell the Prophet ﷺ. Al-Mundhir would not leave the place where his companions had died. Both went in and were captured. Al-Mundhir was killed, and Amr was set free. On his way home, Amr met two men from Amir ibn al-Tufayl's tribe and killed them while they slept. He did not know that the Prophet ﷺ had given them protection. Amr then brought the news of the massacre to Madinah. According to a report in al-Waqidi, the Prophet ﷺ heard of this and of the massacre at al-Raji on the same night. He was deeply grieved. For a whole month he made a special supplication (qunut) in every one of the five daily prayers. He prayed for the martyrs and against the four tribes responsible: Asiya, Ra'l, Dhakwan and Banu Lahyan.
The tribe of Banu Amir ibn Sa'sa'ah had been responsible for the massacre of Muslims at Bi'r Ma'una. They sent a delegation to Madinah, probably in the 7th or 8th year of the Hijrah, before the Conquest of Makkah. With them came Amir ibn al-Tufayl, one of the chief instigators of that massacre. He had no intention of becoming a Muslim. Amir made a plan with his henchman Arbad ibn Qays to kill the Prophet ﷺ. Amir would distract him with questions, and when Amir gave a secret signal, Arbad would stab him, most likely with a poisoned dagger. Amir asked the Prophet ﷺ for a private audience, but the Prophet ﷺ refused unless Amir first embraced Islam. Amir gave the signal three times, and each time Arbad did nothing. Arbad later explained that whenever the signal came, he could see only Amir and not the Prophet ﷺ. When Amir saw that the plot had failed, he offered the Prophet ﷺ three choices. The first was to split the leadership, with the Prophet ﷺ ruling the townspeople and Amir ruling the Bedouins. The second was to name Amir as his successor. Otherwise, Amir would bring an army of a thousand male and a thousand female camels against him. The Prophet ﷺ refused all three. He said, "O Allah, I put You in charge of being sufficient for me against Amir ibn al-Tufayl. O Allah, take care of him and guide his people." Both men met a grim end. On the way home, Amir spent the night at the house of a prostitute and was struck there by a fatal illness. Not wanting to die in such a house, he rode off on his horse into the darkness and was never seen again. Arbad returned to his tribe and said something blasphemous about Allah. The next day, in front of his people, lightning struck and killed both him and his camel. It is said that Qur'an 13:11-13 refers to his fate.