योगवासिष्ठः yogavāsiṣṭhaḥ - book-5, chapter-47, verse-19

मिथो वन्दितसंध्यौ तौ कृतजाप्यावुभावपि ।
क्रमाच्छयनमासाद्य तस्थतुर्मृदुपल्लवम् ॥ १९ ॥

mitho vanditasaṃdhyau tau kṛtajāpyāvubhāvapi ,
kramācchayanamāsādya tasthaturmṛdupallavam 19

19. mithaḥ vanditasandhyau tau kṛtajāpyau ubhau api
kramāt śayanam āsādya tasthatuḥ mṛdupallavam

19. mithaḥ vanditasandhyau kṛtajāpyau ubhau api tau
kramāt mṛdupallavam śayanam āsādya tasthatuḥ

19. Both of them, having mutually performed their twilight prayers and recitations (japa), gradually lay down on a bed of soft sprouts.

Words meanings summery:

• मिथः (mithaḥ) - mutually (mutually, reciprocally, secretly)

• वन्दितसन्ध्यौ (vanditasandhyau) - having performed their twilight prayers ((those who have) saluted/worshipped at twilight)

• तौ (tau) - those two (those two, both of them)

• कृतजाप्यौ (kṛtajāpyau) - having performed their recitations (japa) (having performed japa/recitation)

• उभौ (ubhau) - both (both (dual))

• अपि (api) - also, too (also, even, too)

• क्रमात् (kramāt) - gradually (gradually, in due course, successively)

• शयनम् (śayanam) - bed (bed, couch, lying down, sleep)

• आसाद्य (āsādya) - having reached (having reached, having obtained, having approached)

• तस्थतुः (tasthatuḥ) - they remained (lying down) (they two stood, they two remained, they two rested)

• मृदुपल्लवम् (mṛdupallavam) - a bed of soft sprouts (soft-sprouts, a bed made of soft sprouts)

Words meanings and morphology

मिथः (mithaḥ) - mutually (mutually, reciprocally, secretly)

(indeclinable)

Note: Adverb modifying the actions.

वन्दितसन्ध्यौ (vanditasandhyau) - having performed their twilight prayers ((those who have) saluted/worshipped at twilight)

(adjective)

Nominative, masculine, dual of vanditasandhya

vanditasandhya - having saluted/worshipped at twilight

Bahuvrīhi compound, meaning 'whose sandhyā (twilight prayer) has been saluted/performed'.

Compound type : bahuvrīhi (vandita+sandhyā)

• vandita – saluted, worshipped, praised
  adjective (masculine)
  Past Passive Participle
  From root vand (to salute, praise) + kta suffix.
  Root: vand (class 1)
• sandhyā – twilight, junction, evening/morning prayer
  noun (feminine)
  From prefix sam- + root dhā (to place, join).
  Prefix: sam
  Root: dhā (class 3)

Note: Agrees with tau and ubhau.

तौ (tau) - those two (those two, both of them)

(pronoun)

Nominative, masculine, dual of tad

tad - that, he, she, it

Note: Subject.

कृतजाप्यौ (kṛtajāpyau) - having performed their recitations (japa) (having performed japa/recitation)

(adjective)

Nominative, masculine, dual of kṛtajāpya

kṛtajāpya - one who has performed japa/recitation

Bahuvrīhi compound, 'whose japa has been done'.

Compound type : bahuvrīhi (kṛta+jāpya)

• kṛta – done, made, performed
  adjective (masculine)
  Past Passive Participle
  From root kṛ (to do, make) + kta suffix.
  Root: kṛ (class 8)
• jāpya – recitation, muttering prayers, japa
  noun (neuter)
  Gerundive/Nomen actionis
  From root jap (to mutter, recite). One of the specified terms to be transliterated (japa - a related term).
  Root: jap (class 1)

Note: Agrees with tau and ubhau.

उभौ (ubhau) - both (both (dual))

(pronoun)

Nominative, masculine, dual of ubha

ubha - both

Always occurs in dual number.

अपि (api) - also, too (also, even, too)

(indeclinable)

क्रमात् (kramāt) - gradually (gradually, in due course, successively)

(indeclinable)

From root kram (to step, go).

Root: kram (class 1)

Note: The ablative kramāt often functions as an adverb meaning "in succession, gradually".

शयनम् (śayanam) - bed (bed, couch, lying down, sleep)

(noun)

Accusative, neuter, singular of śayana

śayana - bed, couch, sleep, lying down

Nomen actionis or verbal adjective

From root śī (to lie down, sleep) + -ana suffix.

Root: śī (class 2)

आसाद्य (āsādya) - having reached (having reached, having obtained, having approached)

(indeclinable)

Absolutive (Gerund)

Formed from prefix ā- + root sad (to sit, approach) + suffix -ya.

Prefix: ā

Root: sad (class 1)

Note: Describes the action preceding tasthatuḥ.

तस्थतुः (tasthatuḥ) - they remained (lying down) (they two stood, they two remained, they two rested)

(verb)

3rd person , dual, active, perfect (lit) of sthā

Perfect active indicative

Reduplicated perfect tense.

Root: sthā (class 1)

Note: The dual form matches tau ubhau.

मृदुपल्लवम् (mṛdupallavam) - a bed of soft sprouts (soft-sprouts, a bed made of soft sprouts)

(noun)

Accusative, neuter, singular of mṛdupallava

mṛdupallava - soft sprout, a bed/couch made of soft young leaves/sprouts

Karmadhāraya or Tatpuruṣa compound: mṛdu (soft) + pallava (sprout).

Compound type : karmadhāraya (mṛdu+pallava)

• mṛdu – soft, tender, gentle
  adjective (neuter)
• pallava – sprout, young leaf, bud, twig
  noun (masculine)

Note: Acts as an adjective for śayanam or a direct object if "śayanam" is omitted. Here, it seems to describe the nature of the "śayanam".