It was the tenth year after Hijrat. Islam had emerged as one of the biggest powers in the Arabian Peninsula. After having fought many battles, now Rasool Allah (s) focussed on sending letters and invitations to leaders of the world inviting them towards Islam.
A similar letter was sent to the Christians of Najran, who at that time were the care takers of Kaaba-tul-Najran. This church was so famous that it was called the second Kaaba, after the Kaaba in Mecca.