In this videoconference talk from 13 October 2017, Ajahn Anan discusses the story of our Buddha, when he was a Bodhisattva in a past life, he was a brahmin who gave up his household's only upper garment as a kathina offering.

One can read this talk transcript with Q and A here: https://watmarpjan.org/en/kathina-giving-brightness-of-mind-then-liberation/