What was in the letter the Messenger (saw) sent to Chosroes (Khusru) the ruler of Persia?

Khusru II was one of the most powerful emperors of Persia. In his reign, the Persian Empire reached the pinnacle of its affluence. He even claimed that he was a god in the shape of a man. The Messenger (saw) sent his companion Abdullah bin Huzaifa with a message to Khusru. The Messenger’s letter ran as follows: بسم الله الرحمن الرحيم من محمد رسول الله إلى كسرى عظيم فارس سلام على من اتبع الهدى وامن بالله ورسوله وشهد أن لا اله إلا الله وحده لا شريك له وان محمداً عبده ورسوله وأدعوك بدعاء الله فإني انا رسول الله إلى الناس كافة لأنذر من كان حياً ويحق القول على الكافرين فاسلم تسلم فان ابيت فان إثم المجوس عليك "In the Name of Allah, the Most Beneficent, the Most Merciful. From Muhammad, the Messenger of Allah to Khusru, king of Persia. Peace be upon him who follows true guidance, believes in Allah and His Messenger and testifies that there is no god but Allah Alone with no associate, and that Muhammad is His slave and messenger. I invite you to accept the deen of Allah. I am the Messenger of Allah sent to all people (qawm) that I may infuse fear of Allah in every living person, and the charge may be proved against those who reject the Truth. Accept Islam as your deen so that you may live in security, otherwise, you will be responsible for all the sins of the Magians." When Khusru read the Messenger’s letter, he tore it to pieces, saying: “How dare he write this sort of letter to me when he is my slave?” Khusru then wrote to Bazan who was governor of Yemen, a Persian province. He ordered him to send two soldiers to arrest the Messenger and take him to Persia. Immediately Bazan sent Abadhaweih, one of his assistants, and a Persian officer called Kharkharah, with a warrant which required the Messenger to surrender himself to them and go with them to Khusru. Bazan, however, asked his assistant to find out the truth about the Messenger. Abadhaweih and his companion travelled from Yemen until they arrived in Ta’if, around 100 km from Mecca. Its people told them the Messenger was now in Medina. The people of Ta’if were not Muslims at the time. Quraysh were pleased when they learnt the Persian Emperor had ordered the arrest of Muhammad feeling he was now facing his most difficult test. Clean-shaven but with large moustaches, the two officers from Yemen came to the Messenger in Medina. Abadhaweih said to him: “Khusru, the king of kings, has written to Bazan, the king of Yemen, commanding him to send us to take you to him. If you comply, Bazan will write to the king of kings interceding on your behalf. This will spare you a great deal of trouble. If you reject his order, you know how powerful he is. He is sure to destroy you and your people as well as your country.” The Messenger did not like their appearance. He asked them who ordered them to shave their beards and their reply was: “Our Lord”, meaning Khusru. The Messenger said: “But my Lord has ordered I grow a beard and trim my moustache.” He also asked them to wait till the following day when he was to meet them again. In the meantime, the Messenger (saw) was told by Gabriel that Allah had caused Khusru to be killed by Sherweih, his own son, giving him the exact time of night and the date when Khusru was killed. The Messenger called in the Persian messengers and told them of the killing of their emperor. They said to him: “Do you realize what you are saying? Your arrest has been ordered for something much more trivial than this. Do you still wish us to write this down and inform king Bazan of what you have just said?” The Messenger replied: “Yes. Tell him also on my behalf that my deen and my kingdom will replace that of Khusru and will sweep all before it. Tell him also that if he accepts Islam, I will give him what he has now under his authority and will make him a ruler in the area he now governs.” The Messenger also gave Kharkharah a sack of gold and silver which was sent to him as a present by another king. The two envoys left and went back to Yemen where they told Bazan what the Messenger had said. “This is not the sort of thing a king would say. To my mind, the man is a Messenger, as he claims. If he is, what he has just told you will come to pass. If it is true that Khusru has been killed, the man is a Messenger. If not, we will make up our mind about what to do with him.” In the meantime, Bazan received a message from Sherweih informing him that he had killed his father after he had adopted despotic measures against the Persian nobility. He also commanded him to ask his commanders to swear allegiance to him as the new emperor. He further asked him not to disturb the Messenger until he had received further instructions. Bazan then called Abadhaweih in and questioned him further about the Messenger. The latter told him the Messenger did not keep any guard to protect him from his people or from anyone else. “Nevertheless, I have never spoken to a man who has inspired me with awe as much as he does.” Bazan certain Muhammad (saw) was a Messenger of Allah communicated his conviction to his advisers and counsellors declaring he wished to become a Muslim and they all joined him in accepting the message of the Messenger (saw). (Asqalani, Fath al-Bari)