How to redirect with flash message react-router 4

Here's what i'm trying to achieve: When a user tries to access a protected page on my ReactJS site, i want to redirect them to the home page with a flash message saying "Please log in" or something similar. How do i achieve this with react-router v4. Here's what i have so far:

<Router>
<div>
  <Switch>
    <Route path="/" component={Home} />
    <Route 
      exact path="/source" render={() => (
        isAuthenticated() ? (
          <Source />
        ) : (
          <Home /> //I want to Redirect to the Home Page with a flash message if user is not logged in
        )
      )} 
    />
    <Route path="/contact" component={ContactUs} />
  </Switch>
</div>
</Router>,
);