Dr. Marawan Shahin, Professor of Hadith and its Sciences, Faculty of Usul Ad-Din (Theology),Al-Azhar Univ. states: “The text of the Prophet’s message to Hercules, Caesar, the Negus, etc. read that: In the Name of Allah, Most Gracious, Most Merciful. Accept Islam and you will be secured and Almighty Allah will grant you double reward. If you reject, you will incur the sin of your people.’
It is the same message sent by the Prophet (peace and blessings be upon him) to kings from all corners of the earth. It indicates that being a good example for others and being followed by them in accepting goodness incurs a double reward. On the other hand, being followed in sin and evil will incur one a double sin.
The Prophet’s message to kings never mentioned any threats of launching wars. It also never happened that the Prophet (peace and blessings be upon him) forced any people to accept Islam. Also, in the lifetime of the Prophet (peace and blessings be upon him) armies were sent to the Roman Empire not Persia . And this was because the Romans were gathering armies (200,000 fighters) to launch war against the state of Islam in Madinah. It is not true that `Umar were sent to Persia or that he were told to destroy thousands of books in the libraries as only Islam and the Qur’an were all that what they needed according to your statement. Please refer back to the authentic reliable books of Islamic history to know well how the message of Islam spread whether in the lifetime of the Prophet (peace and blessings be upon him) or after his death uptill now. It was never happened that the Prophet (peace and blessings be upon him) or any of his companions forced any one to embrace Islam. Challenge your colleague that if he could even mention one incident that the Prophet (peace and blessings be upon him) or any of his companions forced any one to accept Islam. Surely, he cannot.”