A Dialog between Maitreyī and Yajñāvalkya [1]
Bṙhadāraṇyaka Upaniṣad 2.4.1 – 14

The sage Yajñāvalkya had two wives: Maitreyī and Katyayānī. Of these, Maitreyī was conversant with the Knowledge of Brahman, while Katyayānī had an essentially worldly outlook.

One day Yajñāvalkya , when he wished to embrace another mode of life, said: “Maitreyī, my dear, I am going to renounce this life to  become a monk. Let me make a final settlement between you and Katyayānī.”

Maitreyī said: “Venerable Sir, if indeed the whole earth full of wealth belonged to me, would I be immortal through that or not?” “No,” replied Yajñāvalkya, “your life would be just like that of people who have plenty. Of Immortality, however, there is no hope through wealth.”  Then Maitreyī said: “What should I do with that which would not make me immortal? Tell me, venerable Sir, of that alone which you know to be the only means of attaining Immortality.”

Yajñāvalkya replied: “My dear, you have been my beloved even before and now you have resolved to know what is after my heart. If you wish, my dear, I shall explain it to you. As I explain it, meditate on what I say.”

Everything is the Self, O Maitreyī!

Yajñāvalkya said:

Verse 2.4.5:

स होवाच: न वा अरे पत्युः कामाय पतिः प्रियो भवति, आत्मनस्तु कामाय पतिः प्रियो भवति । न वा अरे जायायै कामाय जाया प्रिया भवति, आत्मनस्तु कामाय जाया प्रिया भवति । न वा अरे पूत्राणां कामाय पुत्राः प्रिया भवन्ति, आत्मनस्तु कामाय पुत्राः प्रिया भवन्ति । न वा अरे वित्तस्य कामाय वित्तं प्रियं भवति, आत्मनस्तु कामाय वित्तं प्रियं भवति । न वा अरे ब्रह्मणः कामाय ब्रह्म प्रियं भवति, आत्मनस्तु कामाय ब्रह्म प्रियं भवति । न वा अरे क्षत्रस्य कामाय क्षत्रं प्रियं भवति, आत्मनस्तु कामाय क्षत्रं प्रियं भवति । न वा अरे लोकानां कामाय लोकाः प्रिया भवन्ति, आत्मनस्तु कामाय लोकाः प्रिया भवन्ति । न वा अरे देवानां कामाय देवाः प्रिया भवन्ति, आत्मनस्तु कामाय देवाः प्रिया भवन्ति । न वा अरे भूतानां कामाय भूतानि प्रियाणि भवन्ति, आत्मनस्तु कामाय भूतानि प्रियाणि भवन्ति । न वा अरे सर्वस्य कामाय सर्वं प्रियं भवति, आत्मनस्तु कामाय सर्वं प्रियं भवति । आत्मा वा अरे द्रष्टव्यः श्रोतव्यो मन्तव्यो निदिध्यासितव्यो मैत्रेयि, आत्मनो वा अरे दर्शनेन श्रवणेन मत्या विज्ञानेनेदं सर्वं विदितम् ५ ॥

sa hovāca: na vā are patyuḥ kāmāya patiḥ priyo bhavati, ātmanastu kāmāya patiḥ priyo bhavati | na vā are jāyāyai kāmāya jāyā priyā bhavati, ātmanastu kāmāya jāyā priyā bhavati | na vā are pūtrāṇāṃ kāmāya putrāḥ priyā bhavanti, ātmanastu kāmāya putrāḥ priyā bhavanti | na vā are vittasya kāmāya vittaṃ priyaṃ bhavati, ātmanastu kāmāya vittaṃ priyaṃ bhavati | na vā are brahmaṇaḥ kāmāya brahma priyaṃ bhavati, ātmanastu kāmāya brahma priyaṃ bhavati | na vā are kṣatrasya kāmāya kṣatraṃ priyaṃ bhavati, ātmanastu kāmāya kṣatraṃ priyaṃ bhavati | na vā are lokānāṃ kāmāya lokāḥ priyā bhavanti, ātmanastu kāmāya lokāḥ priyā bhavanti | na vā are devānāṃ kāmāya devāḥ priyā bhavanti, ātmanastu kāmāya devāḥ priyā bhavanti | na vā are bhūtānāṃ kāmāya bhūtāni priyāṇi bhavanti, ātmanastu kāmāya bhūtāni priyāṇi bhavanti | na vā are sarvasya kāmāya sarvaṃ priyaṃ bhavati, ātmanastu kāmāya sarvaṃ priyaṃ bhavati | ātmā vā are draṣṭavyaḥ śrotavyo mantavyo nididhyāsitavyo maitreyi, ātmano vā are darśanena śravaṇena matyā vijñānenedaṃ sarvaṃ viditam || 5 ||

“Verily, not for the sake of the husband, my dear, is the husband loved, but he is loved for the sake of the self which, in its true nature, is one with the Supreme Self.  Verily, not for the sake of the wife, my dear, is the wife loved, but she is loved for the sake of the self. Verily, not for the sake of the sons, my dear, are the sons loved, but they are loved for the sake of the self. Verily, not for the sake of wealth, my dear, is wealth loved, but it is loved for the sake of the self.  Verily, not for the sake of the All, my dear, is the All loved, but it is loved for the sake of the self.  

Verily, my dear Maitreyī, it is the Self that should be realized—should be heard of, reflected on and meditated upon.  By the realization of the Self, my dear, through hearing, reflection and meditation, all this is known.

As from a fire kindled with wet fuel various kinds of smoke  issue forth, even so, my dear, the Rig—Veda, the Yajur—Veda,  the Sama—Veda, the Atharvangirasa, history (itihasa),  mythology (purana), the arts (vidya), Upanishads, verses  (slokas), aphorisms (sutras), elucidations (anuvyakhyanas),  explanations (vyakhyanas), sacrifices, oblations in the fire,  food, drink, this world, the next world and all beings are all like  the breath of this infinite Reality. From this Supreme Self are all these, indeed, breathed forth.  

As a lump of salt has neither inside nor outside and is altogether a homogeneous mass of taste, even so this Self, my dear, has neither inside nor outside and is altogether a homogeneous mass of Intelligence. This Self comes out as a separate entity from the elements and with their destruction this separate existence is also destroyed. After attaining this oneness it has no more consciousness. This is what I say, my dear.”  So said Yajñāvalkya.

Then Maitreyī said: “Just here you have completely bewildered me, venerable Sir. Indeed, I do not at all understand this.”  He replied: “Certainly I am not saying anything bewildering, my dear. Verily, this Self is immutable and indestructible. This is quite sufficient for knowledge, O Maitreyī.’

Through what should one know the knower?

यत्र हि द्वैतमिव भवति तदितर इतरं जिघ्रति, तदितर इतरं पश्यति, तदितर इतरम् श्र्णोति,
तदितर इतरमभिवदति, तदितर इतरम् मनुते, तदितर इतरं विजानाति; यत्र वा अस्य सर्वमात्माइवाभूत्तत्केन कं जिघ्रेत्, तत्केन कं पश्येत्, तत्केन कं शृणुयत्, तत्केन कमभिवदेत्, तत्केन कं मन्वीत, तत्केन कं विजानीयात्? येनेदम् सर्वं विजानाति, तं केन विजानीयात्?
विज्ञातारम् अरे केन विजानीयादिति ॥ १४ ॥
इति चतुर्थं ब्राह्मणम् ॥

yatra hi dvaitamiva bhavati taditara itaraṃ jighrati, taditara itaraṃ paśyati, taditara itaram śrṇoti, taditara itaramabhivadati, taditara itaram manute, taditara itaraṃ vijānāti; yatra vā asya sarvamātmāivābhūttatkena kaṃ jighret, tatkena kaṃ paśyet, tatkena kaṃ śṛṇuyat, tatkena kamabhivadet, tatkena kaṃ manvīta, tatkena kaṃ vijānīyāt? yenedam sarvaṃ vijānāti, taṃ kena vijānīyāt? vijñātāram are kena vijānīyāditi || 14 ||
iti caturthaṃ brāhmaṇam ||

“For when there is duality, as it were, then one sees another,  one smells another, one tastes another, one speaks to another,  one hears another, one thinks of another, one touches another,  one knows another. But when to the knower of Brahman everything has become the Self, then what should he see and through what, what should he smell and through what, what should he taste and through what, what should he speak and through what, what should he hear and through what, what should he think and through what, what should he touch and through what, what should he know and through what?  Through what should one know That Owing to which all this is known?

“This Self is That which has been described as ‘Not this, not this.’ It is imperceptible, for It is never perceived; undecaying, for It never decays; unattached, for It never attaches Itself; unfettered, for It never feels pain and never suffers injury.

Through what, O Maitreyī, should one know the Knower?  Bṙhadāraṇyaka Upaniṣad 2.4.14

“Thus you have the instruction given to you. This much, indeed, is the means to Immortality.”

Having said this, Yajñāvalkya departed.

[1] Swāmi Mādhavānanda, trans., The Bṛhadāraṇyaka Upaniṣad with the commentry of Śaṅkarācārya (Mayavati, Almora, Himalayas: Advaita Ashrama, 1934), 347-376.