योगवासिष्ठः yogavāsiṣṭhaḥ - book-7, chapter-158, verse-3

इति तौ चेरतुस्तत्र तपः शास्त्रविचारणैः ।
अकारणसुहृद्भूतावुभौ व्याधमहामुनी ॥ ३ ॥

iti tau ceratustatra tapaḥ śāstravicāraṇaiḥ ,
akāraṇasuhṛdbhūtāvubhau vyādhamahāmunī 3

3. iti tau ceratuḥ tatra tapaḥ śāstravicāraṇaiḥ
akāraṇasuhṛdbhūtau ubhau vyādhamahāmunī

3. iti tatra akāraṇasuhṛdbhūtau ubhau tau
vyādhamahāmunī tapaḥ śāstravicāraṇaiḥ ceratuḥ

3. Thus, those two, the hunter and the great sage, having become friends without any specific cause, lived there practicing asceticism (tapas) and scriptural study.

Words meanings summery:

• इति (iti) - thus (thus, so, in this way (marks reported speech or thought))

• तौ (tau) - those two (the hunter and the sage) (those two, both of them)

• चेरतुः (ceratuḥ) - they two lived (they two wandered, they two lived)

• तत्र (tatra) - there (there, in that place)

• तपः (tapaḥ) - asceticism (tapas) (asceticism, penance, heat)

• शास्त्रविचारणैः (śāstravicāraṇaiḥ) - through scriptural study (by scriptural studies, by deliberations on scriptures)

• अकारणसुहृद्भूतौ (akāraṇasuhṛdbhūtau) - both having become friends without cause (those two who became friends without cause/reason)

• उभौ (ubhau) - both (of them) (both (masculine/neuter dual))

• व्याधमहामुनी (vyādhamahāmunī) - the hunter and the great sage (the hunter and the great sage (dual nominative))

Words meanings and morphology

इति (iti) - thus (thus, so, in this way (marks reported speech or thought))

(indeclinable)

तौ (tau) - those two (the hunter and the sage) (those two, both of them)

(pronoun)

Nominative, masculine, dual of tad

tad - that, he, she, it

Note: Also accusative dual. Nominative fits here as subject.

चेरतुः (ceratuḥ) - they two lived (they two wandered, they two lived)

(verb)

3rd person , dual, active, perfect (liṭ) of car

perfect active

Reduplicated perfect formation

Root: car (class 1)

तत्र (tatra) - there (there, in that place)

(indeclinable)

Formed from tad with -tra suffix

तपः (tapaḥ) - asceticism (tapas) (asceticism, penance, heat)

(noun)

Accusative, neuter, singular of tapas

tapas - heat, penance, asceticism (tapas)

Root: tap (class 1)

शास्त्रविचारणैः (śāstravicāraṇaiḥ) - through scriptural study (by scriptural studies, by deliberations on scriptures)

(noun)

Instrumental, neuter, plural of śāstravicāraṇa

śāstravicāraṇa - deliberation on scriptures, study of scriptures

Compound type : tatpuruṣa (śāstra+vicāraṇa)

• śāstra – scripture, sacred treatise
  noun (neuter)
  From root śās (to command, instruct)
  Root: śās (class 2)
• vicāraṇa – investigation, deliberation, consideration, study
  noun (neuter)
  From vi-car (to move about, examine)
  Prefix: vi
  Root: car (class 1)

Note: Used as means.

अकारणसुहृद्भूतौ (akāraṇasuhṛdbhūtau) - both having become friends without cause (those two who became friends without cause/reason)

(adjective)

Nominative, masculine, dual of akāraṇasuhṛdbhūta

akāraṇasuhṛdbhūta - one who has become a friend without cause

Compound type : bahuvrīhi (akāraṇa+suhṛt+bhūta)

• akāraṇa – without cause, causeless
  adjective
  A-privative compound
• suhṛt – friend, well-wisher
  noun (masculine/feminine)
  From su + hṛd (good heart)
• bhūta – become, been, existing
  adjective
  Past Passive Participle
  From root bhū (to be)
  Root: bhū (class 1)

Note: Qualifies 'tau' and 'vyādhamahāmunī'.

उभौ (ubhau) - both (of them) (both (masculine/neuter dual))

(pronoun)

Nominative, masculine, dual of ubha

ubha - both

Always in dual

Note: Emphatic for 'tau'.

व्याधमहामुनी (vyādhamahāmunī) - the hunter and the great sage (the hunter and the great sage (dual nominative))

(noun)

Nominative, masculine, dual of vyādhamahāmuni

vyādhamahāmuni - hunter and great sage

Dvandva compound

Compound type : dvandva (vyādha+mahāmuni)

• vyādha – hunter, fowler
  noun (masculine)
  Prefixes: vi+ā
• mahāmuni – great sage
  noun (masculine)
  Karmadhāraya compound