BibTeX:
@incollection{BahChronicleseditors,
  author = {Bahá'í Chronicles editors},
  title = {The Gift of the Purest Branch},
  booktitle = {Bahá'í Chronicles},
  url = {https://bahaichronicles.org/mirza-mihdi/},
}

APA:
Bahá'í Chronicles editors. The Gift of the Purest Branch. In *Bahá'í Chronicles*.

MLA:
Bahá'í Chronicles editors. "The Gift of the Purest Branch." *Bahá'í Chronicles*, n.d..

Chicago:
Bahá'í Chronicles editors. "The Gift of the Purest Branch." In *Bahá'í Chronicles*, n.d..