In which episode do fans claim to hear Jensen Ackles accidentally refer to Sam as Jared?

Answer 1

"Provenance"
It's an episode in the first season

When Sam, Dean and Sarah go back into Evelyn's house, Dean is comparing a printout of the painting with the real one and mistakenly says, "Jared, check it out" rather than, "Sam, check it out" (the name of Jared Padalecki's character). Some of the Season One DVDs have fixed this error.

Answer 2

Provenance from season 1
I believe that he says Jared