Musaylimah, whose real name was Maslamah ibn Habib, was a leader of the Banu Hanifa. He was an old man who had studied Christianity in Jerusalem in his youth, and he was respected across the whole region of al-Yamama. In the Year of Delegations he came to Madinah. His followers carried him into the mosque shielded by fine cloth, as if he were a king. He offered to follow the Prophet ﷺ on two conditions: that he be made the Prophet ﷺ's successor, and that he be given a share in prophethood.
The Prophet ﷺ was holding a palm branch at the time. He told Musaylimah that he would not give him even that stick, and that Allah would deal with him. He added that he was certain Musaylimah was what Allah had shown him in a dream. In that dream the Prophet ﷺ saw two gold bracelets on his arms, blew on them, and they flew away. He understood them to be two liars who would appear after him, al-Aswad al-Ansi and Musaylimah of al-Yamama.
When Musaylimah returned home, he wrote a letter to the Prophet ﷺ. He wrote it as one messenger of Allah to another, and claimed that the matter was shared between them, half for the Quraysh and half for him. The Prophet ﷺ asked the two men who brought the letter what they themselves believed, and they said they agreed with it. He told them that, were it not for the rule that envoys are never harmed, he would have had them executed. Musaylimah also made up verses in imitation of the Qur'an, including one about a frog and another about an elephant. One passing Arab told him to his face that they both knew he was a liar.
After the Prophet ﷺ died, many tribes abandoned Islam, and the Muslims fought them in what are called the Ridda (apostasy) wars. The Banu Hanifa were the largest and the worst of these tribes, and they rose behind Musaylimah. In 12 AH the caliph Abu Bakr sent Khalid ibn al-Walid against them. The battle at Yamama was the bloodiest of the Ridda wars.
Among the Muslims who marched was Wahshi, the man who had killed Hamzah at Uhud before he became Muslim. When he heard of the false prophet, he asked Allah to let him take Musaylimah's life in exchange for Hamzah's. He carried the same javelin and threw it at Musaylimah as he had once thrown it at Hamzah. At the same moment, a man of the Ansar struck Musaylimah with a sword from the other side. Wahshi said that only Allah knew which of them had killed Musaylimah.
Many Companions died in the battle. One was Abu Hudhayfah ibn Utbah, who had spoken a sentence at Badr that he regretted for the rest of his life. He used to say he would never feel safe from it unless Allah accepted him as a martyr. Another was Ukasha ibn Mihsan. His sword had broken at Badr, and a stick the Prophet ﷺ handed him became a sword in his hand. He fought with it in every battle until he fell at Yamama.