महाभारतः mahābhārataḥ - book-12, chapter-198, verse-4

यदा निर्गुणमाप्नोति ध्यानं मनसि पूर्वजम् ।
तदा प्रज्ञायते ब्रह्म निकष्यं निकषे यथा ॥४॥

4. yadā nirguṇamāpnoti dhyānaṁ manasi pūrvajam ,
tadā prajñāyate brahma nikaṣyaṁ nikaṣe yathā.

4. yadā nirguṇam āpnoti dhyānam manasi pūrvajam
tadā prajñāyate brahma nikaṣyam nikaṣe yathā

4. yadā manasi nirguṇam pūrvajam dhyānam āpnoti
tadā nikaṣe nikaṣyam yathā brahma prajñāyate

4. When the mind attains primordial contemplation (dhyāna) that is free from attributes, then Brahman (brahman) is truly understood, just as a substance to be tested is discerned on a touchstone.

Words meanings summery:

• यदा (yadā) - when, at which time

• निर्गुणम् (nirguṇam) - describing meditation (dhyāna) (without qualities, attributeless)

• आप्नोति (āpnoti) - attains, reaches, obtains

• ध्यानम् (dhyānam) - primordial meditation (dhyāna) (meditation, contemplation)

• मनसि (manasi) - in the mind

• पूर्वजम् (pūrvajam) - describing meditation (dhyāna) as fundamental or existing from primeval times. (primeval, primordial, ancient, existing before)

• तदा (tadā) - then, at that time

• प्रज्ञायते (prajñāyate) - is truly understood (Brahman) (is known, is understood, is perceived)

• ब्रह्म (brahma) - The ultimate reality that is understood. (Brahman, the ultimate reality, the absolute)

• निकष्यम् (nikaṣyam) - a substance (like gold) that is to be tested. (that which is to be tested, gold to be tested, fit for testing)

• निकषे (nikaṣe) - on a touchstone, on a test

• यथा (yathā) - just as, as, in the manner that

Words meanings and morphology

यदा (yadā) - when, at which time

(indeclinable)

निर्गुणम् (nirguṇam) - describing meditation (dhyāna) (without qualities, attributeless)

(adjective)

Accusative, neuter, singular of nirguṇa

nirguṇa - without qualities, attributeless, transcendent of attributes

Compound type : bahuvrīhi (nis+guṇa)

• nis – without, out, free from
  indeclinable
• guṇa – quality, attribute, constituent of nature
  noun (masculine)

Note: Agrees with dhyānam

आप्नोति (āpnoti) - attains, reaches, obtains

(verb)

3rd person , singular, active, present indicative (laṭ) of āp

Prefix: ā

Root: āp (class 5)

ध्यानम् (dhyānam) - primordial meditation (dhyāna) (meditation, contemplation)

(noun)

Accusative, neuter, singular of dhyāna

dhyāna - meditation, contemplation, thought

derived from √dhyai (to meditate)

Root: dhyai (class 1)

Note: Object of āpnoti

मनसि (manasi) - in the mind

(noun)

Locative, neuter, singular of manas

manas - mind, intellect, thought

Note: Indicates location where meditation occurs

पूर्वजम् (pūrvajam) - describing meditation (dhyāna) as fundamental or existing from primeval times. (primeval, primordial, ancient, existing before)

(adjective)

Accusative, neuter, singular of pūrvaja

pūrvaja - born before, ancient, primeval, prior

Note: Agrees with dhyānam

तदा (tadā) - then, at that time

(indeclinable)

Note: Correlative to yadā

प्रज्ञायते (prajñāyate) - is truly understood (Brahman) (is known, is understood, is perceived)

(verb)

3rd person , singular, passive, present indicative (laṭ) of jñā

passive form of pra-jñā

Prefix: pra

Root: jñā (class 9)

Note: The subject is Brahman.

ब्रह्म (brahma) - The ultimate reality that is understood. (Brahman, the ultimate reality, the absolute)

(noun)

Nominative, neuter, singular of brahman

brahman - Brahman, the absolute, ultimate reality, sacred word

Note: Subject of prajñāyate

निकष्यम् (nikaṣyam) - a substance (like gold) that is to be tested. (that which is to be tested, gold to be tested, fit for testing)

(adjective)

Nominative, neuter, singular of nikaṣya

nikaṣya - to be tested, fit for testing, tested (gold)

Gerundive/Future Passive Participle

derived from √kaṣ (to rub, test) with prefix ni

Prefix: ni

Root: kaṣ (class 1)

Note: Modifies an implied noun like 'gold' or 'substance'

निकषे (nikaṣe) - on a touchstone, on a test

(noun)

Locative, masculine, singular of nikaṣa

nikaṣa - touchstone, test, criterion

Note: Indicates the instrument/place of testing

यथा (yathā) - just as, as, in the manner that

(indeclinable)

Note: Introduces a comparison