During the Conference of Badasht Mulla Husayn was in Mashhad, Khurasan, guest of a brother of Muhammad Shah and the Governor-General of Khurasan - where he was treated with courtesy and consideration. After leaving the camp of the Governor-General, he intended to go to Karbila, but a messenger arrived from the Bab with a Tablet which totally changed his plans. In it the Báb had conferred on him a new name, Siyyid 'Ali, had sent him a green turban of His own to wear, and had directed him to go to Mazindaran to aid and support Quddus [who was under house-arrest], with a black standard unfurled and carried before him. This black standard would be that of which the Prophet Muhammad had given tidings: 'Should your eyes behold the Black Standards proceeding from Khurasan, hasten ye towards them, even though ye should have to crawl over the snow, inasmuch as they proclaim the advent of the promised Mihdi, the Vicegerent of God.'
As soon as that message reached him, Mulla Husayn, the first Letter of the Living, who was acclaimed by Bahá'u'lláh as one 'but for whom God would not have been established upon the seat of His mercy, nor ascended the throne of eternal glory', arose to execute the wishes of his Master. Leaving Mashhad for a place situated at about 12 kilometers from the city, he hoisted the Black Standard, placed the turban of the Báb upon his head, assembled his companions, mounted his steed, and gave the signal for their march towards Mazindaran. His companions, who were two hundred and two in number, enthusiastically followed him. This took place on July 21, 1848!
During this trip they were joined by Bábís who had earlier participated at the conference at Badasht. Wherever they tarried, at every village and hamlet through which they passed, Mulla Husayn and his fellow-disciples would fearlessly proclaim the message of the New Day, would invite the people to embrace its truth, and would select from among those who responded to their call a few whom they would ask to join them on their journey. Thus the number of the companions reached 300 and beyond. This audacious act by Mulla Husayn was” the signal for a clash the reverberations of which were to resound throughout the entire country.”(Shoghi Effendi, God Passes By, p. 38)
It should be noted that during the siege of Fort Tabarsi from about July 1848 to almost end of May 1849, this Black Standard, “that earthly emblem of an unearthly sovereignty waved continually over the heads of that small and valiant band, summoning the multitude who gazed upon it to renounce the world and to espouse the Cause of God.” (Nabil, The Dawn-Breakers, translated and annotated by Shoghi Effendi) (Adapted from God Passes By, by Shoghi Effendi; The Dawn-Breakers, by Nabil; Baha’u’llah King of Glory, by Balyuzi; and The Revelation of Baha’u’llah, vol. 4, by Taherzadeh)