Shaykh Yasir Qadhi picks up the topic of the various letters and emissaries the Prophet ﷺ sent to various rulers after the battle of Khaybar.
The first letter was the letter to Najashi which was a message to accept Islam giving the emperor the promise of Allah forgiving his sins and encouraging him to come to the religion of Allah.
The second letter was sent to Caesar, the emperor of Rome whose name was Heraclius. The Prophet ﷺ wrote to him to submit to the will of Allah and if done, he would be safe. Otherwise, he would have to face the wrath of Allah in one way or the other.
The next letter was sent to the emperor of Persia whose name was Khosrau bearing the same message as the above.
Benefits of these letters:
Every single letter that was sent to a foreign land resulted in the conversion of that land to Islam which was the ultimate divine Qadr of Allah.
The response of the rulers are of theological significance for us.
It is not haraam to imitate the norms of culture and western customs as long as we conform to the Shariah of Islam.