The second person that Quddús met in Shiraz and the Báb’s assignment for him - Mullá Sádiq-i-Khurásání (appointed a Hand of the Cause posthumously by ‘Abdu’l-Baha)

The next person whom Quddús met in Shíráz was Ismu’lláhu’l-Asdaq, Mullá Sádiq-i-Khurásání, to whom he entrusted the copy of the Khasá’il-i-Sab‘ih, [1] and stressed the necessity of putting into effect immediately all its provisions. Among its precepts was the emphatic injunction of the Báb to every loyal believer to add the following words to the traditional formula of the adhán: [2] “I bear witness that He whose name is ‘Alí-Qabl-i-Muhammad [3] is the servant of the Baqíyyatu’lláh.”  [4]

Mullá Sádiq, who in those days had been extolling from the pulpit-top to large audiences the virtues of the imáms of the Faith, was so enraptured by the theme and language of that treatise that he unhesitatingly resolved to carry out all the observances it ordained. Driven by the impelling force inherent in that Tablet, he, one day as he was leading his congregation in prayer in the Masjid-i-Naw, suddenly proclaimed, as he was sounding the adhán, the additional words prescribed by the Báb.  

(Chapter 8, ‘The Dawn-Breakers’)

[1] Literally meaning “The Seven Qualifications.”; [2] Muslim call to prayer; [3] Reference to the name of the Báb; [4] “Remnant of God.” Title applied both to the Báb and to Bahá’u’lláh