महाभारतः mahābhārataḥ - book-7, chapter-16, verse-27

प्रज्वाल्य कृष्णवर्त्मानमुपागम्य रणे व्रतम् ।
तस्मिन्नग्नौ तदा चक्रुः प्रतिज्ञां दृढनिश्चयाः ॥२७॥

27. prajvālya kṛṣṇavartmānamupāgamya raṇe vratam ,
tasminnagnau tadā cakruḥ pratijñāṁ dṛḍhaniścayāḥ.

27. prajvālya kṛṣṇavartmānam upāgamya raṇe vratam
tasmin agnau tadā cakruḥ pratijñām dṛḍhaniścayāḥ

27. dṛḍhaniścayāḥ kṛṣṇavartmānam prajvālya raṇe vratam
upāgamya tadā tasmin agnau pratijñām cakruḥ

27. Having kindled the fire (kṛṣṇavartman) and taken up their battle-vow (vrata), those of firm resolve then made a solemn pledge (pratijñā) in that very fire.

Words meanings summery:

• प्रज्वाल्य (prajvālya) - having kindled, having lit up

• कृष्णवर्त्मानम् (kṛṣṇavartmānam) - Referring to fire. (one whose path is dark/black; the fire)

• उपागम्य (upāgamya) - having approached, having obtained

• रणे (raṇe) - in battle, in combat

• व्रतम् (vratam) - Their vow or sacred duty concerning battle. (a vow, an observance, a sacred duty)

• तस्मिन् (tasmin) - in that

• अग्नौ (agnau) - in the fire

• तदा (tadā) - then, at that time

• चक्रुः (cakruḥ) - they made, they did

• प्रतिज्ञाम् (pratijñām) - a vow, a pledge, a promise

• दृढनिश्चयाः (dṛḍhaniścayāḥ) - those of firm resolve, with firm determination

Words meanings and morphology

प्रज्वाल्य (prajvālya) - having kindled, having lit up

(indeclinable)

absolutive (gerund)

Derived from root jval (to blaze) with prefix pra- and causative suffix -aya, and absolutive suffix -ya.

Prefix: pra

Root: jval (class 1)

कृष्णवर्त्मानम् (kṛṣṇavartmānam) - Referring to fire. (one whose path is dark/black; the fire)

(noun)

Accusative, masculine, singular of kṛṣṇavartman

kṛṣṇavartman - one whose path is dark (due to smoke), an epithet for fire

Compound type : bahuvrīhi (kṛṣṇa+vartman)

• kṛṣṇa – black, dark; Krishna
  adjective (masculine)
• vartman – path, road, track
  noun (neuter)
  Root: vṛt

उपागम्य (upāgamya) - having approached, having obtained

(indeclinable)

absolutive (gerund)

Derived from root gam (to go) with prefixes upa- and ā- and absolutive suffix -ya.

Prefixes: upa+ā

Root: gam (class 1)

रणे (raṇe) - in battle, in combat

(noun)

Locative, masculine, singular of raṇa

raṇa - battle, war, combat, conflict

Root: raṇ (class 1)

व्रतम् (vratam) - Their vow or sacred duty concerning battle. (a vow, an observance, a sacred duty)

(noun)

Accusative, neuter, singular of vrata

vrata - vow, sacred duty, observance, religious practice

Root: vṛ

तस्मिन् (tasmin) - in that

(pronoun)

Locative, masculine, singular of tad

tad - that, he, she, it

Note: Agrees with agnau.

अग्नौ (agnau) - in the fire

(noun)

Locative, masculine, singular of agni

agni - fire, god of fire

तदा (tadā) - then, at that time

(indeclinable)

Derived from tad with the suffix dā.

चक्रुः (cakruḥ) - they made, they did

(verb)

3rd person , plural, active, perfect (lit) of kṛ

Perfect active

3rd person plural perfect active.

Root: kṛ (class 8)

प्रतिज्ञाम् (pratijñām) - a vow, a pledge, a promise

(noun)

Accusative, feminine, singular of pratijñā

pratijñā - a vow, a pledge, an agreement, an assertion

Root: jñā

दृढनिश्चयाः (dṛḍhaniścayāḥ) - those of firm resolve, with firm determination

(adjective)

Nominative, masculine, plural of dṛḍhaniścaya

dṛḍhaniścaya - firm resolve, strong determination, one of firm resolve

Compound type : karmadhāraya (dṛḍha+niścaya)

• dṛḍha – firm, strong, rigid, fixed
  adjective (masculine)
  Root: dṛh
• niścaya – determination, certainty, resolve, decision
  noun (masculine)
  Prefix: nis
  Root: ci

Note: Acts as the subject of cakruḥ.