योगवासिष्ठः yogavāsiṣṭhaḥ - book-2, chapter-14, verse-15

महापदतिदीर्घेषु सद्विचारपरो नरः ।
न निमज्जति मोहेषु तेजोराशिस्तमःस्विव ॥ १५ ॥

mahāpadatidīrgheṣu sadvicāraparo naraḥ ,
na nimajjati moheṣu tejorāśistamaḥsviva 15

15. mahāpadati-dīrgheṣu sat-vicāra-paraḥ naraḥ
na nimajjati moheṣu tejo-rāśiḥ tamaḥsu iva

15. mahāpadati-dīrgheṣu moheṣu sat-vicāra-paraḥ
naraḥ tejo-rāśiḥ tamaḥsu iva na nimajjati

15. A person dedicated to proper discernment (vicāra) does not sink into profound and prolonged delusions (moha), just as a mass of light is not submerged by darkness.

Words meanings summery:

• महापदति-दीर्घेषु (mahāpadati-dīrgheṣu) - in the profound and prolonged (delusions) (in the greatly deep and long, in the profound and prolonged)

• सत्-विचार-परः (sat-vicāra-paraḥ) - dedicated to good discernment, intent on right reflection

• नरः (naraḥ) - a man, a person

• न (na) - not, no

• निमज्जति (nimajjati) - does not sink (into delusions) (sinks, dives, is submerged)

• मोहेषु (moheṣu) - in delusions, in infatuations, in confusions

• तेजो-राशिः (tejo-rāśiḥ) - a mass of light, a heap of brilliance

• तमःसु (tamaḥsu) - in darkness, in gloom

• इव (iva) - like, as, as if

Words meanings and morphology

महापदति-दीर्घेषु (mahāpadati-dīrgheṣu) - in the profound and prolonged (delusions) (in the greatly deep and long, in the profound and prolonged)

(adjective)

Locative, plural of mahāpadati-dīrgha

mahāpadati-dīrgha - greatly deep and long, profound and prolonged

Compound type : karmadhāraya (mahā+padati+dīrgha)

• mahā – great, large, mighty
  adjective
• padati – deep, falling, pertaining to a state/fall
  adjective
  Derived from root pad (to go, fall), here used adjectivally to imply depth or a state of being 'fallen into'.
  Root: pad (class 4)
• dīrgha – long, extensive, prolonged
  adjective

Note: Adjective modifying 'moheṣu'.

सत्-विचार-परः (sat-vicāra-paraḥ) - dedicated to good discernment, intent on right reflection

(adjective)

Nominative, masculine, singular of sat-vicāra-para

sat-vicāra-para - dedicated to good discernment, intent on right reflection

Compound type : tatpuruṣa (sat+vicāra+para)

• sat – good, true, existing
  adjective
• vicāra – discernment, reflection, deliberation, investigation
  noun (masculine)
  Derived from root car with upasarga vi-
  Prefix: vi
  Root: car (class 1)
• para – intent on, devoted to, supreme, other
  adjective (masculine)

Note: Adjective modifying 'naraḥ'.

नरः (naraḥ) - a man, a person

(noun)

Nominative, masculine, singular of nara

nara - man, human being, person

न (na) - not, no

(indeclinable)

निमज्जति (nimajjati) - does not sink (into delusions) (sinks, dives, is submerged)

(verb)

3rd person , singular, active, present (lat) of nimajj

present active

3rd person singular, present tense, active voice, P-root

Prefix: ni

Root: majj (class 6)

मोहेषु (moheṣu) - in delusions, in infatuations, in confusions

(noun)

Locative, masculine, plural of moha

moha - delusion, infatuation, confusion, ignorance

Derived from root muh (to be bewildered, confused)

Root: muh (class 4)

तेजो-राशिः (tejo-rāśiḥ) - a mass of light, a heap of brilliance

(noun)

Nominative, masculine, singular of tejo-rāśi

tejo-rāśi - mass of light, heap of brilliance

Compound type : ṣaṣṭhī-tatpuruṣa (tejas+rāśi)

• tejas – light, brilliance, splendor, energy, spiritual power
  noun (neuter)
• rāśi – heap, pile, mass, quantity
  noun (masculine)

Note: Subject of the simile.

तमःसु (tamaḥsu) - in darkness, in gloom

(noun)

Locative, neuter, plural of tamas

tamas - darkness, gloom, ignorance, one of the three guṇas

इव (iva) - like, as, as if

(indeclinable)

Note: Marks a simile.