Retrieve or Query Pages by ID

I have a problem with my code, I want to display 3 specific pages on my homepage but my code is not working.. here’s the code..

<?php $args = array(
                      'post_type' => 'page',
                      'post__in' => array(3,5,7)
                      );
                    query_posts($args);
                    while (have_posts()) : the_post();
                    $do_not_duplicate = $post->ID; ?>
                <div class ="date_author group">
                    <h3 class="date"><?php the_time('M j, y');?></h3>
                    </div>
                    <h3 class="title"><a STYLE="text-decoration:none" href = "https://wordpress.stackexchange.com/questions/51448/<?php the_permalink();?>"><?php           the_title();?></a></h3>

                    <?php the_excerpt();?>

                    <?php endwhile; ?>

This is an inappropriate use of query_posts() which is only for modifying the main query for the page. Additionally, even if you change your snippet to use get_posts(), your template tags (e.g. the_excerpt()) won’t work as get_posts() isn’t a method of looping through posts, it just returns an array of posts.

What you want is WP_Query. Change your first lines of code to this:

$args = array(
    'post_type' => 'page',
    'post__in' => array(3,5,7)
);
$my_three_posts = new WP_Query( $args );
while ($my_three_posts -> have_posts()) : $my_three_posts -> the_post();
...