In the "Bayan" the Báb says that every religion of the past was fit to become universal. The only reason why they failed to attain that mark was the incompetence of their followers. He then proceeds to give a definite promise that this would not be the fate of the revelation of "Him Whom God would make manifest", that it will become universal and include all the people of the world. This shows that we will ultimately succeed. But could we not, through our shortcomings, failures to sacrifice and reluctance to concentrate our efforts in spreading the Cause, retard the realization of that ideal? And what would that mean? It shall mean that we will be held responsible before God, that the race will remain longer in its state of waywardness, that wars would not be so soon averted, that human suffering will last longer. (From a letter dated 20 February 1932 written on behalf of Shoghi Effendi to an individual believer; The Compilation of Compilations, vol. II, Living the Life)
