Following up after an interview when the promised decision date passes

The interviewer said I'd hear back by Friday. It's now Wednesday of the following week and there's been silence. I know hiring decisions get delayed, but I don't want to sound impatient. I'm drafting a brief follow-up thanking them again and asking whether the timeline has changed. Would you mention the original decision date or simply ask for an update? I'm still interested, just trying to plan other interviews.