BibTeX:
@incollection{AbdulBah1915,
  author = {'Abdu'l-Bahá},
  title = {The Ruby That Was Meant for Medicine},
  booktitle = {Memorials of the Faithful},
  year = {1915},
  publisher = {Bahá'í Publishing Trust},
}

APA:
'Abdu'l-Bahá. (1915). The Ruby That Was Meant for Medicine. In *Memorials of the Faithful*. Bahá'í Publishing Trust.

MLA:
'Abdu'l-Bahá. "The Ruby That Was Meant for Medicine." *Memorials of the Faithful*, Bahá'í Publishing Trust, 1915.

Chicago:
'Abdu'l-Bahá. "The Ruby That Was Meant for Medicine." In *Memorials of the Faithful*, Bahá'í Publishing Trust, 1915.