Mandukya Karika, verse 3.8

Text

यथा भवति बालानां गगनं मलिनं मलैः ।
तथा भवत्यबुद्धानामात्माऽपि मलिनो मलैः ॥ ८ ॥

yathā bhavati bālānāṃ gaganaṃ malinaṃ malaiḥ |
tathā bhavatyabuddhānāmātmā'pi malino malaiḥ || 8 ||

8. As the ether appears to the ignorant children to be soiled by dirt, similarly, the Ātman also is regarded by the ignorant as soiled.

Shankara Bhashya (commentary)

As1 the diversity of experiences such as forms, functions, etc., is caused by the admitted differences of the Ghaṭākāśa, etc., so also is the experience of birth, death, etc., consequent on the perception of the different Jīvas, due to the limitations caused by Avidyā (ignorance). Therefore the contamination of misery, action and result (of action) caused by Avidyā does not really inhere in the Ātman. In order to establish this meaning by an illustration, the text says:—As in our ordinary experience it is found that the ignorant regard the Ākāśa (ether),—which, to those who know, the real nature of a thing by discrimination, is never soiled by any contamination—as soiled with cloud, dust and smoke, so also the Supreme Ātman, the Knower, the innermost Self directly perceived within, is regarded by those who do not know the real nature of the innermost Self, as affected by the evils of misery, action and result. But this is not the case with those who can discriminate. As in the desert are never found foam,2 waves, etc., though thirsty creatures falsely attribute these things to it, similarly the Ātman also is never affected by the turbidity of misery,3 etc., falsely attributed to it by the ignorant.