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After Hudaybiyah, the Holy Prophet (peace and blessings be upon him) sent letters to the rulers of the world. The Caesar of Rome (Hiraql) acknowledged the truth of Islam but did not embrace it due to greed for his kingdom. Kisra of Persia tore the letter — his kingdom was eventually destroyed. The Najashi of Abyssinia showed great respect and embraced Islam. The Muqawqas of Egypt showed great respect, sent precious gifts, but did not embrace Islam.
The Sublime Biography of the Final Messenger of Allah · 107 · Maktaba-tul-Madinah
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