The pot calling the kettle black
A situation where one person accuses someone of or comments on something that they too share
e.g. I treated myself to a nice pair of shoes (for the first time in ages). My sister, who buys herself new clothes EVERY week said I was wasting my money. Honestly! Talk about the pot calling the kettle black.
It is an example of hypocrisy: claiming or believing yourself to be better than you are.