The Báb fulfilled the “Greater Covenant into which… God had, from time immemorial, entered, through the Prophets of all ages, with the whole of mankind, regarding the newborn Revelation”

To this period of incarceration in the fortresses of Máh-Kú and Chihríq—a period of unsurpassed fecundity, yet bitter in its humiliations and ever-deepening sorrows—belong almost all the written references, whether in the form of warnings, appeals or exhortations, which the Báb, in anticipation of the approaching hour of His supreme affliction, felt it necessary to make to the Author of a Revelation that was soon to supersede His own. Conscious from the very beginning of His twofold mission, as the Bearer of a wholly independent Revelation and the Herald of One still greater than His own, He could not content Himself with the vast number of commentaries, of prayers, of laws and ordinances, of dissertations and epistles, of homilies and orations that had incessantly streamed from His pen. The Greater Covenant into which, as affirmed in His writings, God had, from time immemorial, entered, through the Prophets of all ages, with the whole of mankind, regarding the newborn Revelation, had already been fulfilled. 

- Shoghi Effendi  (‘God Passes By’)