September 28

The Guardian would advise, therefore, that henceforth you seek the guidance and approval of the National Spiritual Assembly in all your attempts to refute the criticisms of the enemies of the Cause, as there are certain cases when it is an absolute loss of time and energy, and even perhaps positively harmful, to counteract such attacks, which often lead to interminable and fruitless controversies. The National Spiritual Assembly can best advise you as to what action to take in such matters. 
- Shoghi Effendi  (From a letter dated 28 September 1938 written on behalf of Shoghi Effendi to an individual believer; The Compilation of Compilations, vol. II, Opposition)