Content of Prophet Muhammad S.A.W. letter to Najashi the Negus, king of Abyssinia (Ethiopia) and his reply

 "In the Name of Allâh, the Most Beneficent, the Most Merciful.

From Muhammad the Messenger of Allâh to Negus, king of Abyssinia (Ethiopia). 

Peace be upon him who follows trueguidance. Salutations, I entertain Allâh’s praise, there is no godbut He, the Sovereign, the Holy, the Source of peace, the Giverof peace, the Guardian of faith, the Preserver of safety. I bearwitness that Jesus, the son of Mary, is the spirit of Allâh andHis Word which He cast into Mary, the virgin, the good, thepure, so that she conceived Jesus. Allâh created him from Hisspirit and His breathing as He created Adam by His Hand. Icall you to Allâh Alone with no associate and to His obedienceand to follow me and to believe in that which came to me, for Iam the Messenger of Allâh. I invite you and your men to Allâh,the Glorious, the All-Mighty. I hereby bear witness that I havecommunicated my message and advice. I invite you to listenand accept my advice. Peace be upon him who follows trueguidance."
[Za'd Al-Ma'ad 3/60]

When ‘Amr bin Omaiyah Ad-Damari communicated the Apostolicletter to Negus, the latter took the parchment and placed it on hiseye, descended to the floor, confessed his faith in Islam and wrotethe following reply to the Prophet

"In the Name of Allâh, the Most Beneficent, the Most Merciful.

From Negus Ashama to Muhammad, the Messenger of Allâh.

Peace be upon you, O Messenger of Allâh! and mercy andblessing from Allâh beside Whom there is no god. I havereceived your letter in which you have mentioned about Jesusand by the Lord of heaven and earth, Jesus is not more thanwhat you say. We fully acknowledge that with which you havebeen sent to us and we have entertained your cousin and hiscompanions. I bear witness that you are the Messenger of Allâh, true and confirming (those who have gone before you), Ipledge to you through your cousin and surrender myself through him to the Lord of the worlds."
[Za'd Al-Ma'ad 3/61]