One of the most grant books revealed by Bahá'u'lláh and 'Abdu'l-Bahá. For the first time in any of the revelations there exists a book of the covenant and a will a testament written by the Divine Revelation Himself to his followers, in which He appoints who will guard and protect the cause of God after Him and advices the believers to abide by the teaching and orders as stated in the revealed tablets and prayers.