Arattu (Holy Bath) is a part of the rituals of the festivals of most of the major temples of Kerala, India. In this ritual, the priest takes the Deity form of the god with him and takes a bath in Holy Water. This is mainly carried out at the end of the Festival of the temple.
One of the important Arattu in Kerala is conducted at Padmanabhaswamy Temple, Trivandrum by Travancore royal family
References
Aaraattu Wikipedia(Text) CC BY-SA