and the Prophet made with them a favorable treaty according to which, in return for the payment of taxes, they were to have the full protection of the Islamic state for themselves and their churches and other possessions.
Martin Lings, Muhammad: His Life Based on the Earliest Sources, page 324.
The story of the Christian delegates of Najran is one of my Imam’s favorite stories to tell, since he is a great advocate of interfaith work in our community. I’m so used to hearing this story in khutbahs regularly, that I’m always stunned when Muslims will come up to me and say that interacting with non-Muslims is haraam.
The Prophet (SAW) allowed Christians to pray in a mosque!