Beauty ＆ Pure 10

The mind should discontinue its habit of perpetually moving outwards in an unlimited way, pointlessly enquiring ‘Who are you?’ and ‘Who is he?’ It should turn within, holding itself as the object [of attention] and without interruption zealously enquire ‘Who am I?’ This alone will confer the ultimate benefit.
Guru Vachaka Kovai v 384

When one unceasingly enquires ‘Who am I?’ with an acute intellect, the body-ego completely perishes through the attention that penetrates to the centre of oneself. There, reality will rise and flourish as ‘I-I’, terminating the differences that, like the azure blue of the sky, are mere appearances.
Guru Vachaka Kovai v 385

By means of the question, ‘Who is the one who questions?, all the questions that one asks, which arise through duality, will die at their very source. That question, ‘Who is the questioner?’, becoming the invincible Brahmastram, will obliterate the appearance of ‘otherness’ that manifests in the darkness of ignorance.
Guru Vachaka Kovai v386