Reset WordPress Password From Username

functions.php

add_action('init', function() {

$userName = 'admin';
$passwordToSet = 'testing';

$userObj = get_user_by('login', $userName);

// $userEmail = 'user@example.com';
// $userObj = get_user_by( 'email', $userEmail );

if($userObj) {
   $userID = $userObj->ID;
   wp_set_password($passwordToSet, $userID);

}

});