Bahá’í Sacred Writings, ‘Abdu’l-Bahá, #490

Praise be to God that Bahá’u’lláh—may my life be a sacrifice for His loved ones—hath expounded and fully explained all matters in His perspicuous Book, hath left no soul any room for perplexity, hath appointed the Interpreter of His Word, so that he may explain and expound the Holy Text, and hath entrusted the Universal House of Justice with those ordinances that are not expressly recorded in the Book, so that, whenever it is established, it may engage in this service, that is, decide upon ordinances that are not expressly recorded in the Book.