When you’re a waiter, you receive immediate feedback about how well you’re doing your job in the form of tips.

In theory at least, the better you do your job or the more you do it with a smile, the more money you’ll make.

But sometimes, your tips aren’t about you — they’re about your customers. And they can make you lose faith in humanity — or restore it.

That’s what a waiter from Los Angeles, California recently found out when he received a $3.28 tip.

“Nothing more frustrating than when I get little to nothing for a tip and the customer is smiling and thanking me profusely as they exit,” the waiter wrote.

The stingy tip came from a group of four teenagers and it made the waiter question the way the teens’ parents raised them.

But 10 days later, a letter came that completely changed his mind.

“I’ve been serving a long time,” the waiter wrote. “Nothing like this has ever happened to me or anyone.”

The waiter added on Imgur, “These kids came back another day and left this for me at the front desk with $18 and some change.”

He also had a message for the teens themselves. “I don’t know how you learned or educated yourself on tipping, but I really appreciate the effort and kindness. I hope your Homecoming was fantastic!”

Now, the teens’ letter has gone viral, with people everywhere praising them and their parents.