You can tell who the false prophets are by their deeds.
A good tree produces only good fruit, and a bad tree produces bad fruit. You can tell what a tree is like by the fruit it produces.
You can tell what they are by what they do. No one picks grapes or figs from thornbushes.
You can tell what a tree is like by the fruit it produces. You cannot pick figs or grapes from thornbushes.
So I advise you to stay away from these men. Leave them alone. If what they are planning is something of their own doing, it will fail.
Can a fig tree produce olives or a grapevine produce figs? Does fresh water come from a well full of salt water?