Before meeting the Báb Mulla Husayn had wondered about the significance of Súrih of Joseph in Qur’an

“Mullá Husayn is reported to have said the following: “One day, when I was alone with the late Siyyid [Kázim] in his library, I enquired the reason why the Suriy-i-Yúsúf was entitled in the Qur’án ‘the Best of Stories,’ to which he replied that it was not then the proper occasion for explaining the reason. This incident remained concealed in my mind, neither had I mentioned it to anyone.” 

(“The Taríkh-i-Jadíd,” p. 39.) 
(Footnotes to chapter 3 included by Shoghi Effendi)