dependent upon their connection with Abdul-Baha; for through Him and through Him only, can they receive the spiritual force

The Bahai Faith is THE COVENANT which is in this day established upon the earth, and Abdul-Baha is The Center of this COVENANT. From him all members of it receive spiritual force and sustenance.

As the organs which make up the physical body of man are dependent upon connection with the heart in order that they may receive life force, so are the believers—composing the spiritual body of The Faith—dependent upon their connection with Abdul-Baha; for through Him and through Him only, can they receive the spiritual force and sustenance necessary for their growth and development in The Kingdom.

(SERVICE IN THE KINGDOM, This article was approved by The Center of the Covenant, and some copies in both English and Persian were spread in 1906.)

https://bahai.works/Star_of_the_West/Volume_4/Issue_14/Text