BibTeX:
@incollection{JEEsslemont1923,
  author = {J. E. Esslemont},
  title = {The Month of the Fast: Severance from All Save God},
  booktitle = {Bahá'u'lláh and the New Era},
  year = {1923},
  publisher = {Bahá'í Publishing Trust},
  url = {https://www.bahai.org/library/other-literature/historical/bahaullah-and-the-new-era/},
}

APA:
J. E. Esslemont. (1923). The Month of the Fast: Severance from All Save God. In *Bahá'u'lláh and the New Era*. Bahá'í Publishing Trust.

MLA:
J. E. Esslemont. "The Month of the Fast: Severance from All Save God." *Bahá'u'lláh and the New Era*, Bahá'í Publishing Trust, 1923.

Chicago:
J. E. Esslemont. "The Month of the Fast: Severance from All Save God." In *Bahá'u'lláh and the New Era*, Bahá'í Publishing Trust, 1923.