BibTeX:
@incollection{Various,
  author = {Various},
  title = {The King's Messenger},
  booktitle = {Baha'i Stories for Children},
  url = {https://bahaistoriesforchildren.blogspot.com/2014/12/the-kings-messenger.html},
}

APA:
Various. The King's Messenger. In *Baha'i Stories for Children*.

MLA:
Various. "The King's Messenger." *Baha'i Stories for Children*, n.d..

Chicago:
Various. "The King's Messenger." In *Baha'i Stories for Children*, n.d..