Auth.auth().signIn(withEmail: self.userEmailTextField.text!, password: self.userPasswordTextField.text!) { (user, error) in
  if let user = user {
    print("User has Signed In")
    if user.isEmailVerified {
      self.performSegue(withIdentifier: "toHome", sender: nil)
    } else {
      // do whatever you want to do when user isn't verified
    }
  }
  if let error = error {
    print("Cant Sign in user")
  }
}