महाभारतः mahābhārataḥ - book-5, chapter-123, verse-4

धर्म्यमर्थं महाबाहुराह त्वां तात केशवः ।
तमर्थमभिपद्यस्व मा राजन्नीनशः प्रजाः ॥४॥

4. dharmyamarthaṁ mahābāhurāha tvāṁ tāta keśavaḥ ,
tamarthamabhipadyasva mā rājannīnaśaḥ prajāḥ.

4. dharmyam artham mahābāhuḥ āha tvām tāta keśavaḥ
| tam artham abhipadyasva mā rājan īnaśaḥ prajāḥ

4. O mighty-armed one, dear son, Keśava has spoken to you a purpose (artha) that is in accordance with natural law (dharma). Pursue that purpose, O king; do not destroy your subjects.

Words meanings summery:

• धर्म्यम् (dharmyam) - pertaining to what is righteous and prescribed by natural law (righteous, lawful, in accordance with natural law (dharma), virtuous)

• अर्थम् (artham) - the specific objective or matter being discussed (purpose, object, meaning, wealth, matter, affair)

• महाबाहुः (mahābāhuḥ) - O mighty-armed one (vocative, addressing Dhṛtarāṣṭra) (great-armed, mighty-armed)

• आह (āha) - (he) said (said, spoke)

• त्वाम् (tvām) - to you (you (accusative))

• तात (tāta) - dear son (affectionate address) (dear one, father, son, sir)

• केशवः (keśavaḥ) - Krishna (Keśava (an epithet of Krishna))

• तम् (tam) - that (specific) (that (masculine accusative singular))

• अर्थम् (artham) - that specific objective or matter (purpose, object, meaning, wealth, matter, affair)

• अभिपद्यस्व (abhipadyasva) - pursue, undertake (that purpose) (attain, approach, follow, undertake)

• मा (mā) - do not (not, do not (prohibitive particle))

• राजन् (rājan) - O king (vocative) (king)

• ईनशः (īnaśaḥ) - (you should) destroy (you would destroy, you should destroy)

• प्रजाः (prajāḥ) - your subjects/people (subjects, people, progeny, creatures)

Words meanings and morphology

धर्म्यम् (dharmyam) - pertaining to what is righteous and prescribed by natural law (righteous, lawful, in accordance with natural law (dharma), virtuous)

(adjective)

Accusative, neuter, singular of dharmya

dharmya - righteous, lawful, conformable to dharma, virtuous

From dharma + ya (tad. suffix yat)

अर्थम् (artham) - the specific objective or matter being discussed (purpose, object, meaning, wealth, matter, affair)

(noun)

Accusative, masculine, singular of artha

artha - aim, purpose, meaning, wealth, object, cause

महाबाहुः (mahābāhuḥ) - O mighty-armed one (vocative, addressing Dhṛtarāṣṭra) (great-armed, mighty-armed)

(adjective)

Vocative, masculine, singular of mahābāhu

mahābāhu - mighty-armed, strong-armed

Compound type : bahuvrīhi (mahā+bāhu)

• mahā – great, mighty
  adjective
• bāhu – arm
  noun (masculine)

आह (āha) - (he) said (said, spoke)

(verb)

3rd person , singular, active, perfect (lit) of āha

Perfect tense

Irregular perfect form of √brū (to speak) or √ah

Root: brū (class 2)

त्वाम् (tvām) - to you (you (accusative))

(pronoun)

Accusative, singular of yuṣmad

yuṣmad - you

तात (tāta) - dear son (affectionate address) (dear one, father, son, sir)

(noun)

Vocative, masculine, singular of tāta

tāta - father, son, dear one (term of endearment, often by elder to younger, or among equals)

केशवः (keśavaḥ) - Krishna (Keśava (an epithet of Krishna))

(proper noun)

Nominative, masculine, singular of keśava

keśava - Having beautiful hair; an epithet of Viṣṇu or Kṛṣṇa

तम् (tam) - that (specific) (that (masculine accusative singular))

(pronoun)

Accusative, masculine, singular of tad

tad - that, he, she, it

अर्थम् (artham) - that specific objective or matter (purpose, object, meaning, wealth, matter, affair)

(noun)

Accusative, masculine, singular of artha

artha - aim, purpose, meaning, wealth, object, cause

अभिपद्यस्व (abhipadyasva) - pursue, undertake (that purpose) (attain, approach, follow, undertake)

(verb)

2nd person , singular, middle, imperative (lot) of abhipad

Prefix: abhi

Root: pad (class 4)

मा (mā) - do not (not, do not (prohibitive particle))

(indeclinable)

राजन् (rājan) - O king (vocative) (king)

(noun)

Vocative, masculine, singular of rājan

rājan - king, ruler

ईनशः (īnaśaḥ) - (you should) destroy (you would destroy, you should destroy)

(verb)

2nd person , singular, active, aorist injunctive (luṅ) of naś

Aorist Injunctive

Second person singular aorist injunctive (or subjunctive)

Root: naś (class 4)

प्रजाः (prajāḥ) - your subjects/people (subjects, people, progeny, creatures)

(noun)

Accusative, feminine, plural of prajā

prajā - offspring, progeny, people, subjects, creatures