My Friend Ms Nandhini @yogamaya__
According to Skanda Purana when Raja Indradyumna installed the wooden deities he arranged this bathing ceremony. This day is considered to be the birth-day of Lord jagannath. Held in the full-moon day of the month of Jyestha this festival is also simultaneously held in all other important parts of Puri, it attracts thousands of visitors and pilgrims from all over the country. 'Niladri Mohadaya', a religious text written in Orissan (Oriya) records the rituals of the festival. Sriharsa in his 'naisadhiya Charita' (XV.89) also refers to this festival of Purushottama.
This bathing ceremony has a speciality. As this festival does not find its mention in the early religious texts, it is believed to be a tribal ceremony. Lord. Jagannath in His early form was being worshipped as Nilamadhava by a Savara chief called Viswabasu. The story is nicely told in the drama Jagannath Priyan natakam.
Till now it is the Daitas and Savars (tribals) who have the exclusive right to conduct the festival. The tribals called Saoras (of southern Orissa) still perform a rite to bath their Deities ceremonially on the last day of the month of Jyestha. For this they collect water from remote Jungles where it remains untouched even by the shadow of the animals.