Reference request: Where is this this story about a pair of shoes, a stupa, and virtuous actions?

A teacher told us this story about virtuous actions that goes something like this: > A person passes by a stupa when it is raining. In order to protect the stupa from the rain, they remove their shoes and put them over the stupa. A second person later passes by the same stupa. They see the shoes on the stupa and remove them, thinking that is no place for dirty shoes. **Conclusion:** Both people performed a virtuous action because of their wholesome intentions. Does anyone know where this is from? I believe the teacher mentioned it was from the sutras.