Show body content with popup in Wordpress

$large_image    = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), 'full');

$output .= '<a class="overlay" rel="shadowbox" href="'.$large_image[0].'">';

It's OK, working fine.

But I want, show post's body in popup. I tried like this but not working.

   $content     = wp_get_attachment_image_src( body($post->ID));

Whats the problem? How can I fix it? Thanks.

via Chebli Mohamed