Expired bar soap is safe to use but it's not recommended to do so.
The expired bar soap has a potential to grow bacteria on the soap and the expired bar soap could cause cause skin rashes and sensitivity.
I would not risk the potential rashes or other issues from the bacteria on the expired bar soap.
I usually use bar soap up well before it expires but I would not want to use expired bar soap on my skin as it's not really worth the risk.
But if you have to use the bar of soap that is expired then you can do so but just be aware of the potential for skin rashes.