महाभारतः mahābhārataḥ - book-3, chapter-4, verse-9

पुरोहितपुरोगाश्च तिथिनक्षत्रपर्वसु ।
यज्ञियार्थाः प्रवर्तन्ते विधिमन्त्रप्रमाणतः ॥९॥

9. purohitapurogāśca tithinakṣatraparvasu ,
yajñiyārthāḥ pravartante vidhimantrapramāṇataḥ.

9. purohitapurogāḥ ca tithinakṣatraparvasu
yajñiyārthāḥ pravartante vidhimantrapramāṇataḥ

9. purohitapurogāḥ ca yajñiyārthāḥ tithinakṣatraparvasu
vidhimantrapramāṇataḥ pravartante

9. And led by the family priests, matters concerning the Vedic ritual (yajña) are conducted on auspicious lunar days, stellar mansions, and conjunctions, in accordance with the authority of the prescribed rules and sacred syllables (mantra).

Words meanings summery:

• पुरोहितपुरोगाः (purohitapurogāḥ) - led by the family priests (having chief priests in front, led by chief priests)

• च (ca) - and (and, also)

• तिथिनक्षत्रपर्वसु (tithinakṣatraparvasu) - on auspicious lunar days, stellar mansions, and conjunctions (on lunar days, stellar mansions, and conjunctions/festivals)

• यज्ञियार्थाः (yajñiyārthāḥ) - matters concerning the Vedic ritual (matters relating to Vedic rituals, purposes of Vedic rituals)

• प्रवर्तन्ते (pravartante) - are conducted (they proceed, they are carried out, they begin)

• विधिमन्त्रप्रमाणतः (vidhimantrapramāṇataḥ) - in accordance with the authority of the prescribed rules and sacred syllables (mantra) (according to the authority of rules and sacred syllables)

Words meanings and morphology

पुरोहितपुरोगाः (purohitapurogāḥ) - led by the family priests (having chief priests in front, led by chief priests)

(adjective)

Nominative, masculine, plural of purohitapuroga

purohitapuroga - having priests at the forefront, led by chief priests

Compound type : bahuvrīhi (purohita+puroga)

• purohita – family priest, chaplain, one placed in front
  noun (masculine)
  From puras-√dhā 'to place in front'.
  Prefix: puras
  Root: dhā (class 3)
• puroga – going before, leading, chief, leader
  adjective
  From puras-√gam 'to go before'.
  Prefix: puras
  Root: gam (class 1)

Note: Nominative plural masculine, agreeing with implied subject.

च (ca) - and (and, also)

(indeclinable)

Note: Conjunction.

तिथिनक्षत्रपर्वसु (tithinakṣatraparvasu) - on auspicious lunar days, stellar mansions, and conjunctions (on lunar days, stellar mansions, and conjunctions/festivals)

(noun)

Locative, neuter, plural of tithinakṣatraparvan

tithinakṣatraparvan - lunar days, constellations, and auspicious conjunctions/festivals

Compound type : dvandva (tithi+nakṣatra+parvan)

• tithi – lunar day, a day of the lunar fortnight
  noun (feminine)
• nakṣatra – star, constellation, lunar mansion
  noun (neuter)
• parvan – knot, joint, division, auspicious season, festival, conjunction
  noun (neuter)

Note: Locative plural of tithinakṣatraparvan.

यज्ञियार्थाः (yajñiyārthāḥ) - matters concerning the Vedic ritual (matters relating to Vedic rituals, purposes of Vedic rituals)

(noun)

Nominative, masculine, plural of yajñiyārtha

yajñiyārtha - purpose of a Vedic ritual, matter relating to a Vedic ritual (yajña)

Compound type : tatpuruṣa (yajñiya+artha)

• yajñiya – sacrificial, fit for a Vedic ritual, holy
  adjective
  Derived from yajña.
  Root: yaj (class 1)
• artha – purpose, aim, meaning, matter, thing
  noun (masculine)

Note: Nominative plural masculine.

प्रवर्तन्ते (pravartante) - are conducted (they proceed, they are carried out, they begin)

(verb)

3rd person , plural, middle, present (laṭ) of pravṛt

Prefix: pra

Root: vṛt (class 1)

Note: Present, 3rd person plural, middle voice (ātmanepada) of √vṛt with prefix pra-.

विधिमन्त्रप्रमाणतः (vidhimantrapramāṇataḥ) - in accordance with the authority of the prescribed rules and sacred syllables (mantra) (according to the authority of rules and sacred syllables)

(indeclinable)

Adverb formed with suffix -tas from the compound vidhimantrapramāṇa.

Compound type : tatpuruṣa (vidhi+mantra+pramāṇa)

• vidhi – rule, injunction, ordinance, method, prescribed rite
  noun (masculine)
• mantra – sacred verse, hymn, prayer, sacred formula, incantation
  noun (masculine)
  From √man- 'to think'.
  Root: man (class 4)
• pramāṇa – authority, source of knowledge, proof, standard, measure
  noun (neuter)
  From pra-√mā 'to measure, to prove'.
  Prefix: pra
  Root: mā (class 2)

Note: Adverbial use of ablative -tas.