BibTeX:
@incollection{Various,
  author = {Various},
  title = {Nettie Tobin's Stone},
  booktitle = {Baha'i Stories Blog},
  url = {https://bahaistories.blogspot.com/2015/08/the-stone-that-became-cornerstone-of.html},
}

APA:
Various. Nettie Tobin's Stone. In *Baha'i Stories Blog*.

MLA:
Various. "Nettie Tobin's Stone." *Baha'i Stories Blog*, n.d..

Chicago:
Various. "Nettie Tobin's Stone." In *Baha'i Stories Blog*, n.d..