BibTeX:
@incollection{AbdulBaha1915,
  author = {'Abdu'l-Baha},
  title = {The Brother Who Waited Outside},
  booktitle = {Memorials of the Faithful},
  year = {1915},
  publisher = {Baha'i Publishing Trust},
}

APA:
'Abdu'l-Baha. (1915). The Brother Who Waited Outside. In *Memorials of the Faithful*. Baha'i Publishing Trust.

MLA:
'Abdu'l-Baha. "The Brother Who Waited Outside." *Memorials of the Faithful*, Baha'i Publishing Trust, 1915.

Chicago:
'Abdu'l-Baha. "The Brother Who Waited Outside." In *Memorials of the Faithful*, Baha'i Publishing Trust, 1915.