The incredible volume of the Verses of God revealed by Baha’u’llah during His time in Baghdad -- “in a single day and night, the equivalent of the Qur’án!”

The enormous expansion in the scope and volume of Bahá’u’lláh’s writings, after His return from Sulaymáníyyih, is yet another distinguishing feature of the period under review. The verses that streamed during those years from His pen, described as “a copious rain” by Himself, whether in the form of epistles, exhortations, commentaries, apologies, dissertations, prophecies, prayers, odes or specific Tablets, contributed, to a marked degree, to the reformation and progressive unfoldment of the Bábí community, to the broadening of its outlook, to the expansion of its activities and to the enlightenment of the minds of its members. So prolific was this period, that during the first two years after His return from His retirement, according to the testimony of Nabíl, who was at that time living in Baghdád, the unrecorded verses that streamed from His lips averaged, in a single day and night, the equivalent of the Qur’án! As to those verses which He either dictated or wrote Himself, their number was no less remarkable than either the wealth of material they contained, or the diversity of subjects to which they referred. A vast, and indeed the greater, proportion of these writings were, alas, lost irretrievably to posterity. No less an authority than Mírzá Áqá Ján, Bahá’u’lláh’s amanuensis, affirms, as reported by Nabíl, that by the express order of Bahá’u’lláh, hundreds of thousands of verses, mostly written by His own hand, were obliterated and cast into the river. “Finding me reluctant to execute His orders,” Mírzá Áqá Ján has related to Nabíl, “Bahá’u’lláh would reassure me saying: ‘None is to be found at this time worthy to hear these melodies.’ ...Not once, or twice, but innumerable times, was I commanded to repeat this act.” 
(Shoghi Effendi, ‘God Passes By’)