From Muhammad son of Abu Bakr to the sinner Mu`awiyah son of Sakhr:

Peace of Allah unto those who obey Him from one who is peaceful to whoever accepts only Allah as his Master. 

In His Omnipotence, Greatness, Power and Might, Allah did not create the creation in vain, nor due to a weakness in Him, nor to a need to what He creates. Rather, He created His beings so that they may worship him. He let some of them sin while keeping others on the right guidance. Some of them He left to suffer, and to some He granted happiness. Then He knowingly chose from them Muhammad to be the sole bearer of His Message. He selected him to receive His revelation and entrusted him to carry out His commandments. He sent him as His Messenger, bearer of glad tidings, and warner, to testify to the divine Books which were revealed before his time, and to guide people to uphold His injunctions. So he invited people to accept his mission through wisdom and beautiful exhortation. The first to respond positively to his call, to obey him, to believe in him, to put his all at his disposal, and to be a Muslim, was his brother and cousin Ali ibn Abu Talib (peace be upon him). He believed him with regard to the knowledge of the unknown; he preferred him over everyone else he loved; he protected him with his own life; he solaced him in every precarious situation; he fought those whom he had fought and sought peace with those to whom he was peaceful. He never fled when death seemed imminent out of his love for his life; he came out as one unmatched in prowess; nobody could ever come close to what he undertook. 

I saw how you tried to reach his lofty status, though you are what you are, while he is the one who stood out above the rest as the foremost in the doing of anything good and in embracing Islam. His conviction was most sincere, his offspring the best among all people, his wife the best of all women, whose cousin was the very best, whose brother traded his life on the Day of Mu'ta for the Pleasure of Allah, whose uncle is the master of martyrs on the Day of Uhud, whose father defended the Messenger of Allah and his mission, whereas you are the accursed and the son of the accursed. You and your father have never ceased plotting to undermine the religion of Allah, trying, both of you, to put out the light of Allah, rallying others behind you, spending your wealth and seeking the support of other tribes. 

Thus did your father die, and in his footsteps are you now following. Those who testify against you are the very ones whom you seek to please, while those who resort to you are the pariahs from the remnants of parties, the leaders of hypocrisy, those who are the foremost in dissenting from the Messenger of Allah. Those who testify for Ali, though his virtues are quite obvious and merits eternal, are his supporters whom Allah, the Most Exalted One, mentioned and praised in the Qur'an over all others from the Muhajirs and the Ansars: they are with him battalions and valiant defenders, protecting him with their words, always ready to spill their blood to protect his, finding the truth in following him and perdition in opposing him. 

Woe unto you! How dare you set yourself as an equal to Ali while he is the heir of the Messenger of Allah, his wasi, the father of his offspring, the first among the people to follow him, the very closest to him? He shares with him his secrets; he unfolds his affairs before him, while you are his enemy and the son of his enemy! 

So enjoy your life as long as you can through the means of your falsehood, and let the son of al-As support your sinning, for your end seems to have come close, and your mischief seems to be waning: soon you will come to know who is to receive the lofty rewards! 

And be informed that you are plotting against your own Lord Whose Might you do not fear, from achieving Whose Mercy you have despaired, and He will soon take you by surprise while you remain in the deluge of your conceit. And peace be with whoever follows the right guidance.[270] 

The above quoted letter written by Muhammad son of [first caliph] Abu Bakr contains irrefutable facts of interest to all seekers of the truth. It describes Mu`awiyah as a misguided and misguiding person, as an accursed and the son of an accursed man, and that he tries by all might and means to put Allah's light out, spending wealth to distort the creed, plotting against Allah's religion, and that he is the enemy of Allah and His Messenger who deals with falsehood assisted by Amr ibn al-As. 

This letter also unveils the virtues and merits of Ali (peace be upon him) which nobody else could claim in the past nor can anyone achieve in the future. In fact, Ali ibn Abu Talib (peace be upon him) has more virtues and merits than what Muhammad ibn Abu Bakr has counted here, but what concerns us most in this chapter is the answer he received from Mu`awiyah ibn Abu Sufyan. Such an answer will acquaint the seeker of the truth with what is hidden and plotted in history. We will uncover, once we read it, the threads of the plot that kept the caliphate out of the reach of its legitimate owner and that caused the nation to deviate; so, let us provide you with his answer.