How did the teachings and narrations of the Messenger, may Allah's peace and blessings be upon him, reach the people outside the Arabian Peninsula?

The teachings and hadiths of the Prophet, peace be upon him, reached outside the Arabian Peninsula through the dispatch of envoys and expeditions. He sent fifty-six expeditions (sariyyah) and twenty-seven campaigns (ghazwah) for the call to God. His teachings also reached them through his letters to kings, such as Heraclius, Khosrow, Negus, and Muqawqis.