BibTeX:
@incollection{Various,
  author = {Various},
  title = {A Knighthood for the Master},
  booktitle = {Baha'i Stories for Children},
  url = {https://bahaistoriesforchildren.blogspot.com/2017/06/abdul-baha-knight-of-light.html},
}

APA:
Various. A Knighthood for the Master. In *Baha'i Stories for Children*.

MLA:
Various. "A Knighthood for the Master." *Baha'i Stories for Children*, n.d..

Chicago:
Various. "A Knighthood for the Master." In *Baha'i Stories for Children*, n.d..