What was in the letter the Messenger (saw) sent to Jaifer the ruler of Oman?

The Messenger (saw) sent the following letter to Jaifer and his brother: "In the Name of Allah, the Most Beneficent, the Most Merciful. From Muhammad bin Abdullah to Jaifer and Abd al-Jalandi. Peace be upon him who follows true guidance; thereafter I invite both of you to the Call of Islam. Embrace Islam. Allah has sent me as a Messenger (saw) to all His creatures in order that I may instil fear of Allah in the hearts of His disobedient creatures so that there may be left no excuse for those who deny Allah. If you two accept Islam, you will remain in command of your country; but if you refuse my call, you’ve got to remember that all your possessions are perishable. My horsemen will appropriate your land, and my messengerhood will assume preponderance over your kingship." Amr bin al-As, who was chosen to carry the letter, narrated the following story that happened before he was admitted into the audience of Jaifer. He narrated: "When I arrived in Oman, I contacted Abd, who was known to be more mild-tempered than his brother: Amr: I am the envoy of Allah’s Messenger coming to see both, you and your brother. Abd: You have to see my brother and read to him the letter you are carrying. He is my senior in both age and kingship. While we're on the subject, what is the purport of your mission? Amr: The Messenger calls upon you to believe in Allah Alone with no associate, discard any other deities and testify to the slavehood and messengerhood of Muhammad. Abd: O Amr! You come from a noble family, but first of all, tell me what was your father’s attitude concerning this faith? You know, we used to follow his steps. Amr: Death overtook him before believing in Muhammad’s deen; I wish now he had embraced Islam and been truthful to it before his death. I myself had adopted the same attitude until Allah guided me towards Islam. Abd: When did you embrace Islam? Amr: When I was at Negus’s court. By the way, the latter did also enter into the fold of Islam. Abd: What was his people’s reaction? Amr: They approved of him and followed his steps. Abd: The bishop? Amr: They did the same. Abd: Beware Amr of lying, for this soon betrays man. Amr: I never tell lies; moreover, our deen never allows it. Abd: Has Hercules been informed of the Islamisation of Negus? Amr: Yes, of course. Abd: How did you happen to know that? Amr: Negus used to pay land tax to Hercules, but when the former embraced Islam, he swore he would discontinue that tax. When this news reached Hercules, his courtiers urged him to take action against Negus but he refused and added he himself would do the same if he were not sparing of his kingship. Abd: What does your Messenger exhort you to do? Amr: He exhorts us to obey Allah, the All-Mighty, and All-Glorious, be pious and maintain good ties with family kin; he forbids disobedience, aggression, adultery, wine, idolatry and devotion to the cross. Abd: Fair words and fair beliefs are those you are calling for. I wish my brother would follow me to believe in Muhammad (saw) and profess his religion, but my brother is too sparing of his kingship to become a subordinate. Amr: Should your brother surrender himself to Islam, the Messenger (saw) would give him authority over his people and take alms tax from the wealthy people to be given to the needy. Abd: That is fair behavior. But what is this alms tax you have mentioned? Amr: It is a Divine injunction that alms tax be taken from the well-to-do people who have surplus wealth and be distributed to the poor. Abd: I doubt if this can work among our people. Amr stayed for some days to be admitted into Jaifer’s court until he was finally granted this permit. "He asked me to hand him the letter to read it. After that he asked me how Quraysh reacted and I answered that they had followed him, some out of their own freewill and others overpowered by military fighting. Now, people have chosen Islam in preference to other creeds, and have realized through their mental insight that they had been straying in darkness. None, except you, is now out of the domain of Islam, so I advise you to embrace Islam so that you can provide security to yourself and your country." Here, he asked me to call on him the following day. The following day he showed some reluctance in receiving me but his brother ‘Abd’ interceded and I was given the chance to see him again but this time to address me in a threatening arrogant tone. However, after a private talk with his brother and reconsidering the whole situation, both brothers embraced Islam and proved to be true to Islam that had begun to make its way into this new area. The context of this story reveals that this letter was sent at a much later date than the others, most likely after the conquest of Mecca.