Show Only 5 Blog Posts on Home Page

gistfile1.php

<?php
/***************************************************************
* Function wpmark_alter_homepage_posts_query()
* Alter query on homepage for show just 5 posts
***************************************************************/
function wpmark_alter_homepage_posts_query( $query ) {

	/* check this is not the main query, the admin - if so bail early */
	if( ! $query->is_main_query() || is_admin() )
		return;
	
	/* check whether this is the job post type archive or a job tax archive */
	if( is_home() ) {
		
		/* set job archives to show 10 posts per page */
		$query->set( 'posts_per_page', 5 );
		
	}
	
	return;

}

add_action( 'pre_get_posts', 'wpmark_alter_homepage_posts_query', 10 );