с мусульманами

with Muslims

→ с
phrase Rare #46,918
with Muslims The preposition с meaning “with” is used with the instrumental case; мусульманами is the instrumental plural form of мусульманин.
RU: Я часто общаюсь с мусульманами из разных стран.
EN: I often communicate with Muslims from different countries.

Они имеют дело с мусульманами.

They are dealing with Muslims.

С мусульманами договорился?

Did you reach an agreement with the Muslims?

— Пророк (2009)