Therefore the knowledge of this Self by the process of ‘Not this, not this’ and the renunciation of everything are the only means of attaining immortality . . . The discussion of the knowledge of Brahman, culminating in renunciation, is finished. This much is the instruction, this is the teaching of the Vedas, this is the ultimate goal, this is the end of what a man should do to achieve his highest good.
– Sankara’s Bhasya on Brhadaranyaka Up 4.5.15
I can think of no better contemporary commentary on the essence of Sankara’s meaning than the words of Sri Nisargadatta Maharaj.
From the very beginning of ‘I am that’, on neti, neti:
“Give up all questions except one: ‘Who am I?’ After all, the only fact you are sure of is that you are. The ‘I am’ is certain. The ‘I am this’ is not. Struggle to find out what you are in reality.
To know what you are, you must first investigate and know what you are not.
Discover all that you are not — body, feelings thoughts, time, space, this or that — nothing, concrete or abstract, which you perceive can be you. The very act of perceiving shows that you are not what you perceive.
The clearer you understand on the level of mind you can be described in negative terms only, the quicker will you come to the end of your search and realise that you are the limitless being.”
On desirelessness and earnestness / one-pointedness:
“All desires must be given up, because by desiring you take the shape of your desires. When no desires remain, you revert to your natural state.”
“The desire to find the self will be surely fulfilled, provided you want nothing else. But you must be honest with yourself and really want nothing else. If in the meantime you want many other things and are engaged in their pursuit, your main purpose may be delayed until you grow wiser and cease being torn between contradictory urges. Go within, without swerving, without ever looking outward.”
On renunciation and liberation:
“When there is total surrender, complete relinquishment of all concern with one’s past, present and future, with one’s physical and spiritual security and standing, life dawns full of love and beauty; then the guru is not important for the disciple has broken the shell of self-defence. Complete self-surrender by itself is liberation.”
“To be quiet and detached, beyond the reach of all self-concern, all selfish consideration, is an inescapable condition of liberation. You may call it death; to me it is living at its most meaningful and intense, for I am one with life in its totality and fullness.”
“In matters of daily life, the knower of the real has no advantage; he may be at a disadvantage rather – being freed from greed and fear he does not protect himself. The very idea of profit is foreign to him; he abhors accretions; his life is constant divesting oneself, sharing, giving. Give up all and you gain all. Then life becomes what it is meant to be: pure radiation from an inexhaustible source.”