Add a Custom message with the post insertion redirect in wordpress.

custom post edit message.php

add_filter('wp_insert_post_data', 'ccl', 99);
function ccl($data) {
  if ($data['post_type'] !== 'revision' && $data['post_status'] == 'publish') {
    $data['post_status'] = 'draft';
    add_filter('redirect_post_location', 'my_redirect_post_location_filter', 99);
  }
  return $data;
}
Then add a message variable in the redirect filter function.

function my_redirect_post_location_filter($location) {
  remove_filter('redirect_post_location', __FUNCTION__, 99);
  $location = add_query_arg('message', 99, $location);
  return $location;
}
Finally hook into the post_updated_messages filter and add your message so Wordpress knows what to print.

add_filter('post_updated_messages', 'my_post_updated_messages_filter');
function my_post_updated_messages_filter($messages) {
  $messages['post'][99] = 'Publish not allowed';
  return $messages;
}