What follows is my provisional translation (in other words, not official or authorized; see here for more) of a passage from a letter by Shoghi Effendi dated April 1927 and addressed to the Spiritual Assemblies of various Eastern countries. The original Persian text of this passage has been published in Tawqíʻát-i-Mubárakih (1927–1939), pp. 26–27.
My spiritual brothers! With the shedding of His most pure blood, the Báb—may the lives of all beings be a sacrifice for the wrongs He suffered—cleansed the outworn attire of this contingent realm from the deep-seated stains that had, with the passing of thousands of years, embedded themselves upon its surface, and sanctified the robe of the world from the defilements of prejudice and blind imitation that had once smirched it. The raging fire ignited by His grievous martyrdom has utterly ravaged each and every one of the foundations upon which rest every antiquated belief, every erroneous principle, and every outmoded delusion. It has, moreover, spared the soil of men’s hearts from the briars and brambles of such attachments, doubts, fancies, and imaginings as belong to this realm of dust, and in so doing prepared the means for that soil to receive the outpourings of heavenly grace—those limitless effulgences shed by the Promised Sun [Baháʼuʼlláh].
A typescript of the original Persian text of this passage appears below.