BibTeX:
@incollection{Various,
  author = {Various},
  title = {Revelation in the Síyáh-Chál},
  booktitle = {bahaistories.com archive},
  url = {https://bahaistories.com/subject/siyah-chal-bahaullahs-declaration},
}

APA:
Various. Revelation in the Síyáh-Chál. In *bahaistories.com archive*.

MLA:
Various. "Revelation in the Síyáh-Chál." *bahaistories.com archive*, n.d..

Chicago:
Various. "Revelation in the Síyáh-Chál." In *bahaistories.com archive*, n.d..