Hide the contents for specific post

Your code doesn’t seem to be trying to hide the content, but you can use the_content filter to return an empty content if you are on a specific post page. For example:

add_filter('the_content', 'hide_post_contents');

function hide_post_contents( $content ) {
   if( is_single(3) ) {
        return '';
    }
    return $content;
}

Also, there is a mistype in your code. funcion must be changed to function.