Is it forbidden to bring animals (cats) into the mosque?

Cats are pure, and their entry into the mosque does not cause harm, based on the Prophet's (peace be upon him) saying: "They are not impure; they are among those who frequently circulate among you." However, if they cause harm or if the mosque becomes soiled by their fur, they should be kept away. This is especially true if there is a fear of the mosque being defiled by their urine or excrement, in which case their entry becomes forbidden.