April 21

During the latter days [passed] in Adrianople Bahá’u’lláh composed a detailed epistle setting forth all matters clearly and minutely. He unfolded and expounded the main principles of the sect, and made clear and plain its ethics, manners, course, and mode of conduct: He treated certain political questions in detail, and adduced sundry proofs of His truthfulness: He declared the good intent, loyalty, and sincerity of the sect, and wrote some fragments of prayers, some in Persian, but the greater part in Arabic. He then placed it in a packet and adorned its address with the royal name of His Majesty the King of Persia, and wrote [on it] that some person pure of heart and pure of life, dedicated to God, and prepared for martyr-sacrifice, must, with perfect resignation and willingness, convey this epistle into the presence of the King. A youth named Mírzá Badí, a native of Khurásán, took the epistle, and hastened toward the presence of His Majesty the King. 
(‘Abdu’l-Baha, ‘A Traveler’s Narrative’)