There is nothing that brings success in the Faith like service. Service is the magnet which draws the divine confirmations. Thus, when a person is active, they are blessed by the Holy Spirit. When they are inactive, the Holy Spirit cannot find a repository in their being, and thus they are deprived of its healing and quickening rays.
-Shoghi Effendi (From a letter written on behalf of Shoghi Effendi, 12 July 1952 to an individual believer; The Compilation of Compilations, vol. I, Baha’i Funds and Contributions)