Pūjā or worship of a deity, whether in a temple or at home, is an elaborate ritual. This pūjā can be based either on the Vedic traditions or on the tāntric.
One of the preliminary processes in a tāntric pūjā is ‘bhūtaśuddhi’ or purification of the elements, making up the body of the worshipper.
The worshipper has to raise his own self, the jīvātman, first to the feet of the Lord (Paramaśiva or Paramātman) dwelling in the sahasrāra or thousand petalled lotus in the head. Then, uttering the mantra yaṁ, has to imagine that the dross in his body has dried up. This should be followed by the burning up this dross through the mantra raṁ. The drossless body is then to be bathed in ambrosia, uttering the mantra vaṁ and completely regenerated by the mantra laṁ. This purified and regenerated body is now fit to worship the Lord.
This whole process is called ‘bhūtaśuddhi.’