Here is a little excerpt, from the story of Musailamah the liar ... 
And the letter he wrote to the Prophet (SAW)

One day the south of the Arab Peninsula witnessed the emergence of two 
Presumptuous and arrogant liars 
Who claimed prophethood 
And tried to drag people into the swamp of sin and disbelief ... 

One of these impostors was called Al-Aswad Ibn Ka'b Al `Aansiy, from San'aa ... 
The other was Musailamah the Liar from Al Yamaamah ... 

Both impostors incited people against the believers in their tribes 
Who responded to what Allah ordained and who believed in His Prophet ... 

They also goaded them against the Prophet's messengers 
Whom he sent to their lands ... 
Moreover, they even went so far as to ignite suspicion against prophethood itself 
And committed hideous mischief in the land 
Causing corruption and disbelief ...

One day, the Prophet (PBUH) was surprised when a messenger arrived 
With a message from Musailamah in which he said:

From Musailamah Allah's Prophet to Muhammad Allah's Prophet ... 
Peace be upon you ... 
We are your partner in prophethood ... 
Consequently, we have half of the earth ...
And the Quraish has the other half ... 
But the Quraish want unjustly to have it all ...

The Prophet (PBUH) summoned one of his scribes 
And dictated this answer to Musailamah:

In the name of Allah 
The Most Beneficient
The Most Merciful
From Muhammad the Prophet of Allah to Musailamah the Liar ... 
Peace be upon those who followed the right path ... 
Verily, the earth is Allah's ... 
He gives it as a heritage to whom He will of His slaves ... 
And the blessed end is for the pious and righteous persons who fear Allah ...