Here's an exert from the email that the HR recruiter sent to one of my references:
I recently had the privilege of interviewing X for a position with our organization and Iím continuing to bring him through the interview process.
The next step on our end is to complete X's professional references. X indicated you would be available for me to reach in order to discuss the work history you have in common with him.
Please let me know when you are available to speak over the phone. It would be great to catch up with you as soon as possible.