CC Ādi 17.18
yathā tathā bhakta-gaṇa dekhila viśeṣe
After this incident, the Lord remained in an ecstatic position for twenty-one hours, and all the devotees saw His specific pastimes.
In the Deity’s room there must be a bed for the Deity behind His throne. (This system should immediately be introduced in all our centers. It does not matter whether the bed is big or small; it should be of a size the Deity room can conveniently accommodate, but there must be at least a small bed.) One day in the house of Śrīvāsa Ṭhākura, Lord Caitanya Mahāprabhu sat down on the bed of Viṣṇu, and all the devotees worshiped Him with the Vedic mantras of the Puruṣa-sūkta, beginning with sahasra-śīrṣā puruṣaḥ sahasrākṣaḥ sahasra-pāt. This veda-stuti should also be introduced, if possible, for installations of Deities. While bathing the Deity, all the priests and devotees must chant this Puruṣa-sūkta and offer the appropriate paraphernalia for worshiping the Deity, such as flowers, fruits, incense, ārati paraphernalia, naivedya, vastra and ornaments. All the devotees worshiped Lord Caitanya Mahāprabhu in this way, and the Lord remained in ecstasy for seven praharas, or twenty-one hours. He took this opportunity to show the devotees that He is the original Supreme Personality of Godhead, Kṛṣṇa, who is the source of all other incarnations, as confirmed in the Bhagavad-gītā (10.8): ahaṁ sarvasya prabhavo mattaḥ sarvaṁ pravartate. All the different forms of the Supreme Personality of Godhead, or viṣṇu-tattva, emanate from the body of Lord Kṛṣṇa. Lord Caitanya Mahāprabhu exposed all the private desires of the devotees, and thus all of them became fully confident that Lord Caitanya is the Supreme Personality of Godhead.
Some devotees call this exhibition of ecstasy by the Lord sāta-prahariyā bhāva, or “the ecstasy of twenty-one hours,” and others call it mahābhāva-prakāśa or mahā-prakāśa. There is a description of this sāta-prahariyā bhāva in the Caitanya-bhāgavata, Madhya-khaṇḍa, chapter nine, which mentions that Śrī Caitanya Mahāprabhu blessed a maidservant named Duḥkhī with the name Sukhī. He called for Kholāvecā Śrīdhara and showed him His mahā-prakāśa. Then He called for Murāri Gupta and showed him His feature as Lord Rāmacandra. He offered His blessings to Haridāsa Ṭhākura, and at this time He also asked Advaita Prabhu to explain the Bhagavad-gītā as it is (gītāra satya-pāṭha) and showed special favor to Mukunda.