I once heard a story from a monk of two brothers, Culapandaka and Mahapandaka, one of which was very bright while the other was slow. I believe one of the brothers receives a special meditation object from the Buddha, perhaps focusing on cleaning with a piece of cloth? I’m likely butchering the story but this is just the gist of what I remember. I’d be very grateful if someone could point me to the right direction where I could read the original source of this story. Is it a sutta? Or perhaps commentary? I tried to do a search on the site but I wasn’t able to find anything.