The Man from Earth is a 2007 science fiction written by Jerome Bixby.
There are links here to sites where you can view the film online.
It's certainly not an original concept. I've seen it done several times, including by Star Trek.
Locus Magazine has a review here.
SFSignal has a review, which closes, "the exploration of the experience of immortality is what this film is about - and ultimately that makes The Man from Earth is a film worth watching".