"Khalid wrote more harshly to the Sassanian rulers: “From Khalid b. al-Walid to the rulers of the Persians: Peace be upon whosoever follows right guidance.”30 This was to become the mandated greeting for Muslims toward non-Muslims; when greeting a fellow Muslim, Muslims were to say, “Peace be upon you.” But to a non-Muslim, a Muslim was to wish peace only upon “whoever follows right guidance,” that is, the Muslims. Khalid continued: Praise be to God, Who has scattered your servants, wrested your sovereignty away, and rendered your plotting weak. Whoever worships the way we worship, faces the direction we face in prayer, and eats meat slaughtered in our fashion, that person is a Muslim and obtains the benefits we enjoy and takes up the responsibilities we bear. Now then, when you receive this letter, send me hostages and place yourself under my protection. Otherwise, by Him other than Whom there is no god, I will most certainly send against you a people who love death just as you love life. The Sassanian rulers soon realized these were not empty words. Khalid stormed through Persia, offering the Persians the same ultimatum: convert to Islam, pay the jizya, or face war. He defeated the Persians in numerous battles."