Al-Qasim (may Allah have mercy on him) said: Someone came to Sayyiduna Abdullah (may Allah be pleased with him) (bin Mas'ud) and said to him: O Abu Abdur Rahman! There are some people here who recite the recitation of Musaylimah. Sayyiduna Abdullah (may Allah be pleased with him) turned him away. He stayed away for as long as Allah willed, then that man came to him again and said: By the One by whom I swear, O Abu Abdur Rahman! I have just left them in a house, and that mushaf is still with them. So Sayyiduna Abdullah (may Allah be pleased with him) gave orders to Qarazah bin Ka'b, who set off with people accompanying him, and he said: "Bring them." When they were brought, Sayyiduna Abdullah (may Allah be pleased with him) said: "What is this, after Islam has spread far and wide?" They said: O Abu Abdur Rahman! We seek Allah's forgiveness and repent to Him, and we bear witness that Musaylimah is the liar who fabricates lies against Allah and His Messenger. So Sayyiduna Abdullah (may Allah be pleased with him) had them repent and sent them away to Syria; they were about eighty men. Ibn al-Nawwahah refused to repent, so he gave the order to Qarazah bin Ka'b, who took him out to the marketplace and struck off his neck, and he ordered him to take his head and throw it into his mother's lap. Abdur Rahman bin Abdullah said: Later I met an old man among them in Syria, and he said: May Allah have mercy on your father! By Allah, had we been killed that day, all of us would have entered the Fire.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8928