BibTeX:
@incollection{Various,
  author = {Various},
  title = {The story of how Abdu’l-Bahá blessed May and Sutherland Maxwell with a child – Mary (Ruhiyyih Khanum)},
  booktitle = {Baha'i Stories Blog},
  url = {https://bahaistories.blogspot.com/2015/03/the-story-of-how-abdul-baha-blessed-may.html},
}

APA:
Various. The story of how Abdu’l-Bahá blessed May and Sutherland Maxwell with a child – Mary (Ruhiyyih Khanum). In *Baha'i Stories Blog*.

MLA:
Various. "The story of how Abdu’l-Bahá blessed May and Sutherland Maxwell with a child – Mary (Ruhiyyih Khanum)." *Baha'i Stories Blog*, n.d..

Chicago:
Various. "The story of how Abdu’l-Bahá blessed May and Sutherland Maxwell with a child – Mary (Ruhiyyih Khanum)." In *Baha'i Stories Blog*, n.d..