This man did not deny that Muhammad (PBUH) was the Prophet of God...
This man did not deny that Muhammad (PBUH) was the Prophet of God; he claimed that God had appointed him as a co- prophet with Muhammad to share his task. The letter which had addressed to the Holy Prophet just before the Mussailama''s death reads: "From Musailma the prophet of God to Muhammad the Prophet of God(PBUH).
I wish to inform you that I have been appointed as your partner to share in the burden of prophethood." The historian Tabari has recorded a tradition which says that the call to prayers''(Adhan) which Musailama had devised for his followers included the words, "I testify that Muhammad is the Prophet of God." Despite Musailama''s clear affirmation of the Prophethood of Muhammad (PBUH), he was declared an apostate and ostracised from the society of Islam.
Not only this but a war was waged on Musailama. History also bears witness to the fact that the tribe of Hunaifa (Banu Hunaif) had accepted Musailama''s claim to prophethood in good faith. They had been genuinely led to believe that Muhammad (PBUH) had of his own accord declared Musailama as his partner in prophethood. A man who had learnt Qur''an in the Holy City of Medina went to the tribe of Banu Hunaifa and falsely represented the verses of the Qur''an as having been revealed to Musailama.
Though Banu Hunaifa had been deliberately misinformed, nevertheless the companions of the Holy Prophet did not recognize them as muslims and sent an army against them. There is no scope here for taking the view that the companions had fought against them as rebels and not as apostates. Islamic Law lays down that in the event of a war against the rebel Muslims, the prisoners taken in battle shall not be taken into slavery.
The law further requires that even the rebellious Dhimmis, when taken as prisoners in battle, shall not go into slavery. But when military action was taken against Musailama and his followers, Hadrat Abu Bakr declared that the women and children of the enemy would be taken as slaves; and when they were taken prisoner in battle, they were enslaved. From among these a girl was given as a slave to Hadrat Ali.
She bore him a son named Muhammad bin Hanfiya, who is a renowned figure in the history of Islam. (Al- Badaya wan-Nihaya, Vol. VI, pp. 316 & 325) This event is a clear proof of the fact that when companions fought against Musailama, they did not charge him with rebellion.