BibTeX:
@incollection{Various,
  author = {Various},
  title = {To Mrs Smith, a new Bahá’í, who belonged to a distinguished Philadelphia family},
  booktitle = {bahaistories.com archive},
  url = {https://bahaistories.com/subject/happiness},
}

APA:
Various. To Mrs Smith, a new Bahá’í, who belonged to a distinguished Philadelphia family. In *bahaistories.com archive*.

MLA:
Various. "To Mrs Smith, a new Bahá’í, who belonged to a distinguished Philadelphia family." *bahaistories.com archive*, n.d..

Chicago:
Various. "To Mrs Smith, a new Bahá’í, who belonged to a distinguished Philadelphia family." In *bahaistories.com archive*, n.d..