BibTeX:
@incollection{Bahullh1891,
  author = {Bahá'u'lláh},
  title = {The Epistle Recalls the Síyáh-Chál},
  booktitle = {Epistle to the Son of the Wolf},
  year = {1891},
  publisher = {Bahá'í Publishing Trust},
  url = {https://www.bahai.org/library/authoritative-texts/bahaullah/epistle-son-wolf/},
}

APA:
Bahá'u'lláh. (1891). The Epistle Recalls the Síyáh-Chál. In *Epistle to the Son of the Wolf*. Bahá'í Publishing Trust.

MLA:
Bahá'u'lláh. "The Epistle Recalls the Síyáh-Chál." *Epistle to the Son of the Wolf*, Bahá'í Publishing Trust, 1891.

Chicago:
Bahá'u'lláh. "The Epistle Recalls the Síyáh-Chál." In *Epistle to the Son of the Wolf*, Bahá'í Publishing Trust, 1891.