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Reference: WordPress Codex — Custom Taxonomies > Querying by taxonomy

Creating a taxonomy generally automatically creates a special query variable using WP_Query class, which we can use to retrieve posts based on. For example, to pull a list of posts that have “Bob” as a “person” taxonomy in them, we will use:

$query = new WP_Query( array( 'person' => 'bob' ) );

or, for more complex argument:

$args = array(
    'tax_query' => array(
        array(
            'taxonomy' => 'person',
            'field' => 'slug',
            'terms' => 'bob'
        )
    )
);
$query = new WP_Query( $args );

What’s above is quoted from the document I linked far above, and I think it’s very very relevant/close to what you are doing.

Solution:

<?php query_posts(array( 'post_type' => 'sermon', 'sermon_series' => $sermon_series )); ?>
<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>

<div class="post">
    <h2><a href="https://wordpress.stackexchange.com/questions/58720/<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>
    <small><?php the_time('F jS, Y') ?></small>
</div>

<?php endwhile; ?>
<?php endif; ?>

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