Definition
This idiom advises against criticizing others for flaws or faults that one possesses themselves.
He always criticizes others' mistakes, yet he often makes the same ones himself; it's a classic case of 'people who live in glass houses shouldn't throw stones'.
Before you criticize her work style, you should examine your own; remember, 'people who live in glass houses shouldn't throw stones'.
She shouldn't be so harsh on her colleague for being late, as she is often late herself; it's a clear case of 'people who live in glass houses shouldn't throw stones'.