get_the_excerpt by ID post

functions.php

<?php
/**
 * Filter from "the_excerpt".
 *
 * @since 1.0.0
 * @param string $post_excerpt The post excerpt.
 *
 */
function get_excerpt_by_ID( $post = 0){
    $post = get_post( $post );

    if ( empty( $post ) ) {
        return '';
    }

    if ( post_password_required() ) {
        return __( 'There is no excerpt because this is a protected post.' );
    }

    return apply_filters( 'get_the_excerpt', $post->post_excerpt );
}

/**
 * Filter the displayed post excerpt.
 *
 * @since 1.0.0
 * @see get_excerpt_by_ID()
 * @param string $post_excerpt The post excerpt.
 *
 */
function the_excerpt_by_ID( $post = 0){
    echo apply_filters( 'the_excerpt', get_excerpt_by_ID( $post ) );
}