code: protected function attemptLogin(Request $request)
      {
          if ($this->guard()->validate($this->credentials($request))) {
              $user = $this->guard()->getLastAttempted();
  
              if (! is_null($user->confirmed_at)) {
                  return $this->baseAttemptLogin($request);
              }
  
              session([
                  'confirmation_user_id' => $user->getKey()
              ]);
  
              throw ValidationException::withMessages([
                  'confirmation' => [
                      __('confirmation::confirmation.not_confirmed', [
                          'resend_link' => route('auth.resend_confirmation')
                      ])
                  ]
              ]);
          }
          return false;
      }
docs: Attempt to log the user into the application.
  
  @param  \Illuminate\Http\Request $request
  @return bool
  @throws ValidationException