BibTeX:
@incollection{MrzMamdiZarqn1998,
  author = {Mírzá Maḥmúd-i-Zarqání},
  title = {A Gift for Every Servant},
  booktitle = {Mahmúd's Diary},
  year = {1998},
  publisher = {George Ronald},
  url = {https://bahai-library.com/zarqani_mahmuds_diary},
}

APA:
Mírzá Maḥmúd-i-Zarqání. (1998). A Gift for Every Servant. In *Mahmúd's Diary*. George Ronald.

MLA:
Mírzá Maḥmúd-i-Zarqání. "A Gift for Every Servant." *Mahmúd's Diary*, George Ronald, 1998.

Chicago:
Mírzá Maḥmúd-i-Zarqání. "A Gift for Every Servant." In *Mahmúd's Diary*, George Ronald, 1998.