References when my manager was laid off too after 4 years as an insurance claims processor

My manager was laid off too and I am unsure who to use as a reference. I have one former client who liked my work. How do you ask politely?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.

Ask former colleagues and supervisors in a short message and give them a summary of the job you are applying for.