Quran represents the Islamic greeting of peace as a universal greeting. They advance their argument on the basis of the following texts:

O you who believe, enter not into houses other than yours without first announcing your presence and invoking peace (saying salaam) upon the folk thereof. That is better for you, that you may be heedful

And servants of (Allah) the Most Gracious are those who walk on the earth in humility, and when the ignorant address them, they say, Peace (Salaam)!

Consider his cry: O my Lord! Surely they are a people who do not believe! So turn away from them and say Salaam (Peace) for they shall soon come to know.

Also, And when they hear ill speech, they turn away from it and say, For us are our deeds and for you are your deeds, peace be upon you; we seek not the ignorant