All the information have taken from different internet sources. So it is highly recommended to make research yourself before to believe it. If i'm wrong anywhere, please correct me. Thank you;
Letter of Prophet Muhammad (peace be upon Him) to Qaisar e Roam (kings of Roam use the surname "Qaisar" for them selves). (NOTE: This is not the handwriting of Prophet Muhammad (peace be upon
Him). Our Prophet was "Umaee". So his companions write letters on His
command. He use to dictate them.
