Passing a variables to a template part using get_template_part()

some-file.php

<?php
// Set up the variable(s) to be passed as an associative array
// NOTE: it MUST be an associative array for this to work, because of the 'extract()' function to be used
$variables = [
  'text' => 'See you on the other side!'
];

// Pass the array along with a reference name using the 'set_query_var()' function
// This function basically passes variables via a URL query string
set_query_var( 'passed-variables', $variables );

// Get the template part as normal
get_template_part('template-part');

template-part.php

<?php
// In the template part, we need to retrieve the passed variables
// Use the 'get_query_var()' function to get the passed values by their reference name
$passed = get_query_var('passed-variables');

// Now use the native PHP 'extract()' to turn the array into variables
// This should be familiar if you have ever created custom shortcodes
// Because the 'extract()' function only works with an associative array, is does not hurt to ensure that the retrieved variable is indeed an array, otherwise an error will occur
if ( is_array($passed) ) {
  extract($passed);
}

// The extracted variables can now be used as normal variables
?>
<p><?php echo $text; ?></p>