get sources term with name cf_section

// WP_Term_Query arguments
$args = array(
	'taxonomy'               => array( 'sources' ),
	'name'                   => array( '$cf_section' ),
	'hierarchical'           => true,
	'childless'              => false,
	'fields'                 => 'id=>slug',
	'get'                    => 'all',
);

// The Term Query
$sources_section = new WP_Term_Query( $args );