BibTeX:
@incollection{Various,
  author = {Various},
  title = {At the close of his talk, ‘Abdu’l-Bahá made a practical demonstration},
  booktitle = {bahaistories.com archive},
  url = {https://bahaistories.com/subject/generosity},
}

APA:
Various. At the close of his talk, ‘Abdu’l-Bahá made a practical demonstration. In *bahaistories.com archive*.

MLA:
Various. "At the close of his talk, ‘Abdu’l-Bahá made a practical demonstration." *bahaistories.com archive*, n.d..

Chicago:
Various. "At the close of his talk, ‘Abdu’l-Bahá made a practical demonstration." In *bahaistories.com archive*, n.d..