In Star Wars: The Last Jedi, Luke tells Rey he's going to give her three lessons - lessons about why the Jedi have to end, as he says in the trailer. The movie features two of them and now we know what happened to the third.
/Film has the exclusive details, which include an elaborate scene involving the Ahch-To Caretakers and a famous shot from the behind-the-scenes footage released this summer. The entire sequence was filmed but cut from the final product.
According to the site, which confirmed the information with multiple sources, after Luke and Rey talk about the history of the Jedi, boats are seen coming to Ahch-To. Rey inquires and Luke says they're bandits who regularly terrorize the Caretakers. Outraged, Rey says she wants to help, but Luke tells her if she helps, they will come back stronger and in greater numbers next time. A true Jedi would let it happen and keep the balance.
Rey disagrees and runs to the village, as seen in the above shot taken from the behind-the-scenes footage. When she gets there, lightsaber ignited, she realises Luke lied. It's not bandits, it's a party, one that Chewie is enjoying along with the porgs, R2-D2, and others. Rey feels relieved but betrayed.
Luke tells her he's sorry but that's the third lesson. That real help comes from action, not the mystery of some old religion. Unamused, Rey reportedly cries and says "that old legend of Luke Skywalker that you hate so much, I believed in it." Luke is ashamed of himself.
According to the article, this was cut because it painted Luke in an even worse light. It was also supposed to be partially funny and maybe the humour didn't quite work. But you also have to think the scene would have lengthened an already long movie -- and was maybe not as impactful as intended, considering what comes later. It also serves a similar purpose as Rey finding out the truth about Ben before she eventually leaves the island anyway.
This scene might make it onto the Blu-ray, though, as director Rian Johnson has already teased there may be upwards of 20 minutes of deleted scenes. Other scenes could include a few moments on Canto Bight (including a bathhouse scene detailed here) and different versions of Finn, Rose, and DJ arriving on Snoke's ship. Read more about them at the below link.