Dear Sir,
Purity of mind is attainment of Clarity - தெளிவு Thelivu
That discernment which does not give rise to any doubts, is the purification, bathing in the Ganges.
when this clarity is discerned, even when there is Maya, it will not shake the 'Chaitanya' like how Janaka was not shaken when he saw his entire kingdom destroyed by fire. The Moon (body) and Chaitanya, when discerned as the Self, then, even when big meteorites or moon quakes hit the moon, the Light is not affected, like wise, what what happens in the body, will never bother such a chaitanya.
That clarity, which results is no fear, doubts, aversions, joy, judgement, and that because of which, everything is at poise, samatva, unperturbed, that wisdom is cleansing. Discernment of that wisdom is the annihilation of ego.
Upon that discernment, ego, has no place to stand, it is annihilated altogether, and, the annihilation is more, just an inference, there is really no annihilation, as it was itself that danced as the ego, and has now ceased to be.
When such a clarity has dawned, there is no way one can be under the sway of the mind/ego any more. What ever such a one does, does so as a Leela - Divine play.
ॐ