BibTeX:
@incollection{Various,
  author = {Various},
  title = {The miracle of the Báb’s last day},
  booktitle = {Baha'i Stories for Children},
  url = {https://bahaistoriesforchildren.blogspot.com/2020/05/the-miracle-of-babs-last-day.html},
}

APA:
Various. The miracle of the Báb’s last day. In *Baha'i Stories for Children*.

MLA:
Various. "The miracle of the Báb’s last day." *Baha'i Stories for Children*, n.d..

Chicago:
Various. "The miracle of the Báb’s last day." In *Baha'i Stories for Children*, n.d..