BibTeX:
@incollection{Various,
  author = {Various},
  title = {Quddús's Commentary on a Single Letter},
  booktitle = {Baha'i Stories Blog},
  url = {https://bahaistories.blogspot.com/2018/01/quddus-amazing-ability-to-pen-copious.html},
}

APA:
Various. Quddús's Commentary on a Single Letter. In *Baha'i Stories Blog*.

MLA:
Various. "Quddús's Commentary on a Single Letter." *Baha'i Stories Blog*, n.d..

Chicago:
Various. "Quddús's Commentary on a Single Letter." In *Baha'i Stories Blog*, n.d..