Rebbe who trade olam habah for lulav and esrog?

When i was a kid I remember a rabbi telling me a story about a rebbe who traded his olam habah for a lulav and esrog (there is more to the story but I don’t remember it, just the punchline/lesson) and when asked “what’s the point of shaking the lulav and esrog if the schar (reward) is all going to someone else?” And the rabbi replying, “for the first time ever, I get to do a mitzvah not for reward but purely because I want to fulfill God’s command.”

For the life of me I can’t remember any other details about this story or if its actually true. I would appreciate any information/links to help 🙏