BibTeX:
@incollection{Various,
  author = {Various},
  title = {Faithful Isfandíyár},
  booktitle = {Baha'i Stories for Children},
  url = {https://bahaistoriesforchildren.blogspot.com/2015/02/faithful-isfandiyar.html},
}

APA:
Various. Faithful Isfandíyár. In *Baha'i Stories for Children*.

MLA:
Various. "Faithful Isfandíyár." *Baha'i Stories for Children*, n.d..

Chicago:
Various. "Faithful Isfandíyár." In *Baha'i Stories for Children*, n.d..