Adding validation to existing forms using #element_validate
the method that work is this

function MYMODULE_form_NODE_FORMID_alter(&amp;$form, &amp;$form_state) {
  dpm($form);
  $form['body'][LANGUAGE_NONE][0][['#element_validate'][] = 'MYMODULE_validate_breads_node_form_alter';
}

/**
 * Implements callback function().
 * Specific alteration for views exposed forms
 */
function MYMODULE_validate_NODE_FORMID_alter($element, &amp;$form, &amp;$form_state) {
  if (empty($element['#value'])) {
    form_error($element, t('Text'));
  }
}