This is a reference to the arrival of Bahá'u'lláh and His companions in the Najíbíyyih Garden outside the city of Baghdád, subsequently referred to by the Bahá'ís as the Garden of Ridván. This event, which took place thirty-one days after Naw-Rúz, in April 1863, signalized the commencement of the period during which Bahá'u'lláh declared His Mission to His companions. In a Tablet, He refers to His Declaration as "the Day of supreme felicity" and He describes the Garden of Ridván as "the Spot from which He shed upon the whole of creation the splendours of His Name, the All-Merciful". Bahá'u'lláh spent twelve days in this Garden prior to departing for Istanbul, the place to which He had been banished.
The Declaration of Bahá'u'lláh is celebrated annually by the twelve-day Ridván Festival, described by Shoghi Effendi as "the holiest and most significant of all Bahá'í festivals" (see notes 138 and 140).