योगवासिष्ठः yogavāsiṣṭhaḥ - book-6, chapter-64, verse-20

तदासावेकनिष्ठत्वाभावात्तन्नाशयेद्द्वयम् ।
तस्मादेकार्थनिष्ठत्वाद्भिक्षुजीवेन रुद्रताम् ॥ २० ॥

tadāsāvekaniṣṭhatvābhāvāttannāśayeddvayam ,
tasmādekārthaniṣṭhatvādbhikṣujīvena rudratām 20

20. tadā asau ekaniṣṭhatvābhāvāt tat nāśayet dvayam
| tasmāt ekārthaniṣṭhatvāt bhikṣujīvena rudratām

20. tadā asau ekaniṣṭhatvābhāvāt tat dvayam nāśayet tasmāt
ekārthaniṣṭhatvāt bhikṣujīvena rudratām (prāpnoti)

20. Then that person, due to a lack of single-minded focus (ekaniṣṭhatva), would thereby destroy both (the intention and the intellect). Therefore, through steadfast devotion to a single object (ekārthaniṣṭhatva), the renunciate (bhikṣu) living being (jīva) attains the state of Rudra (rudratā).

Words meanings summery:

• तदा (tadā) - then, at that time, in that case

• असौ (asau) - that one, he, she

• एकनिष्ठत्वाभावात् (ekaniṣṭhatvābhāvāt) - due to the absence of single-mindedness/fixation on one object

• तत् (tat) - that (intention) (that, it; thus (adverbial))

• नाशयेत् (nāśayet) - would destroy, should destroy, might destroy

• द्वयम् (dvayam) - a pair, duality, two

• तस्मात् (tasmāt) - therefore, thence, from that

• एकार्थनिष्ठत्वात् (ekārthaniṣṭhatvāt) - due to fixation on a single object/meaning

• भिक्षुजीवेन (bhikṣujīvena) - by the living being (jīva) who is a renunciate (bhikṣu)

• रुद्रताम् (rudratām) - the state of Rudra, Rudrahood (rudratā)

Words meanings and morphology

तदा (tadā) - then, at that time, in that case

(indeclinable)

असौ (asau) - that one, he, she

(pronoun)

Nominative, masculine, singular of adas

adas - that (demonstrative pronoun)

एकनिष्ठत्वाभावात् (ekaniṣṭhatvābhāvāt) - due to the absence of single-mindedness/fixation on one object

(noun)

Ablative, masculine, singular of ekaniṣṭhatvābhāva

ekaniṣṭhatvābhāva - lack of single-minded devotion

Compound type : Tatpurusha (eka+niṣṭhatva+abhāva)

• eka – one, single
  numeral (masculine)
• niṣṭhatva – the state of being fixed/devoted to, steadfastness
  noun (neuter)
  Derived from niṣṭha (fixed) + tva (suffix for 'state of being')
• abhāva – absence, non-existence, non-being
  noun (masculine)
  Negative prefix a- + bhāva (being)
  Prefix: a

तत् (tat) - that (intention) (that, it; thus (adverbial))

(pronoun)

Accusative, neuter, singular of tad

tad - that (demonstrative pronoun)

नाशयेत् (nāśayet) - would destroy, should destroy, might destroy

(verb)

3rd person , singular, active, optative (Vidhiliṅ) of nāś

Causative, Optative Mood

Root naś (4th class, to perish) with causative suffix -aya. Optative (Potential Mood)

Root: naś (class 4)

द्वयम् (dvayam) - a pair, duality, two

(noun)

Accusative, neuter, singular of dvaya

dvaya - a pair, two, duality

तस्मात् (tasmāt) - therefore, thence, from that

(indeclinable)

Note: Ablative case used adverbially

एकार्थनिष्ठत्वात् (ekārthaniṣṭhatvāt) - due to fixation on a single object/meaning

(noun)

Ablative, neuter, singular of ekārthaniṣṭhatva

ekārthaniṣṭhatva - the state of being fixed on a single object/meaning

Compound type : Tatpurusha (eka+artha+niṣṭhatva)

• eka – one, single
  numeral (masculine)
• artha – object, meaning, purpose
  noun (masculine)
• niṣṭhatva – the state of being fixed/devoted to, steadfastness
  noun (neuter)
  Derived from niṣṭha (fixed) + tva (suffix for 'state of being')

भिक्षुजीवेन (bhikṣujīvena) - by the living being (jīva) who is a renunciate (bhikṣu)

(noun)

Instrumental, masculine, singular of bhikṣujīva

bhikṣujīva - a renunciate living being

Compound type : Karmadhāraya (bhikṣu+jīva)

• bhikṣu – mendicant, renunciate, beggar
  noun (masculine)
  Root: bhikṣ (class 1)
• jīva – living being, individual soul (jīva)
  noun (masculine)
  Root: jīv (class 1)

रुद्रताम् (rudratām) - the state of Rudra, Rudrahood (rudratā)

(noun)

Accusative, feminine, singular of rudratā

rudratā - the state of Rudra, Rudrahood

Derived from Rudra + tā (suffix for 'state of')