وكتب إلى النجاشي بسم الله الرحمن الرحيم من محمد رسول الله إلى النجاشي ملك الحبشة أسلم أنت فإني أحمد إليك الله الذي لا إله إلا هو الملك القدوس السلام المؤمن المُهَيمن وأشهد أن عيسى إبن مريم روح الله وكلمته القاها إلى مريم البتول الطيبة الحصينة فحملت بعيسى فخلقه من روحه ونفخه كما خلق آدم بيده واني أدعوك إلى الله وحده لا شريك له والمُوالاة على طاعته وأن تتّبعني وتؤمن بالذي جاءني فاني رسول الله واني أدعوك وجنودك إلى الله عز وجل وقد نلّغتُ ونصحت فاقبلوا نصيحتي والسلام على من إتبع الهدى
زاد المعاد لإبن قيم الجهاد والغزوات فصل ذكر هديه ﷺ في مكاتباته إلى الملوك وغيرهم
And He wrote to Najashi: In the name of Allah the Merciful the Compassionate, from Muhammad the Messenger of Allah to Najashi king of Abyssinia: Yield into Islam you! Indeed I praise Allah for you, He besides who there is no god, the Holy King, Giver of Peace, Granter of Security, the Protector, and I bear witness that ‘Isa son of Maryam is the spirit of Allah and His word that He cast onto Maryam the pleasant and well-protected virgin, who carried ‘Isa; He created him from His spirit and His breath, just as He created Adam by His hand. Indeed I call you to Allah alone, none associated with Him, to be constant in obedience to Him, and to follow me and to believe in what has come to me, for indeed I am the Messenger of Allah, and indeed I call you and your armies to Allah Mighty and Sublime; I have given you the news and have advised you, so take my advice. Peace to those who follow guidance.
Ibn Qayyim, Zad Al-Ma’ad, Jihad and Raids, Section: mention of his (SAW) guidance in his correspondence with kings and others