In plain words
Drona, Bhishma, Jayadratha, Karna, and the other heroic warriors have already been struck down by Me. Slay them; do not be distressed. Fight—you will conquer your enemies in battle.
Word for word
Droṇa and Bhīṣma and Jayadratha and Karṇa, and likewise the other heroic warriors too, slain by Me: you slay [them]; do not be afraid; fight; you will conquer [your] rivals in battle.
द्रोणं च भीष्मं च जयद्रथं चकर्णं तथाऽन्यानपि योधवीरान्मया हतांस्त्वं जहि मा व्यथिष्ठायुध्यस्व जेतासि रणे सपत्नान्
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam· bhāṣya
द्रोणं च, येषु येषु योधेषु अर्जुनस्य आशङ्का तांस्तान् व्यपदिशति भगवान् , मया हतानिति । तत्र द्रोणभीष्मयोः तावत् प्रसिद्धम् आशङ्काकारणम् । द्रोणस्तु धनुर्वेदाचार्यः दिव्यास्त्रसम्पन्नः, आत्मनश्च विशेषतः गुरुः गरिष्ठः । भीष्मश्च स्वच्छन्दमृत्युः दिव्यास्त्रसम्पन्नश्च परशुरामेण द्वन्द्वयुद्धम् अगमत् , न च पराजितः । तथा जयद्रथः, यस्य पिता तपः चरति ‘मम पुत्रस्य शिरः भूमौ निपातयिष्यति यः, तस्यापि शिरः पतिष्यति’ इति । कर्णोऽपि वासवदत्तया शक्त्या त्वमोघया सम्पन्नः सूर्यपुत्रः कानीनः यतः, अतः तन्नाम्नैव निर्देशः । मया हतान् त्वं जहि निमित्तमात्रेण । मा व्यथिष्ठाः तेभ्यः भयं मा कार्षीः । युध्यस्व जेतासि दुर्योधनप्रभृतीन् रणे युद्धे सपत्नान् शत्रून् ॥ ३४ ॥
In plain words
And Droṇa too — whichever warrior worries you, that is exactly the one I name as already slain by me. Droṇa and Bhīṣma, at least, are easy to understand: Droṇa is the very master of the science of archery, armed with celestial weapons, and above all he is your own most venerable teacher. Bhīṣma can choose the very hour of his own death, wields divine weapons too, once fought Paraśurāma himself in single combat and was never beaten. Jayadratha is protected because his father's austerity won a boon: whoever makes his son's head fall to the ground will have his own head fall the same way. And Karṇa carries an unfailing weapon given by Indra himself — he is truly the Sun's own son, though born before his mother's marriage, which is why he is named that way here. All of them are already slain by me. You are only the occasion. So do not grieve over them, do not be afraid — fight, and you will win, against Duryodhana and every rival who stands against you.
Close to the Sanskrit
And Droṇa — in whichever, whichever warriors there is Arjuna's apprehension, those very ones the Lord specifies by name, saying 'slain by me.' There, regarding Droṇa and Bhīṣma at least, the reason for apprehension is well-known. Droṇa indeed is the teacher of the science of archery, endowed with divine weapons, and moreover specially the most venerable guru of Arjuna himself. And Bhīṣma, whose death occurs only by his own will, and who is endowed with divine weapons, engaged in single combat with Paraśurāma, and was not defeated. Likewise Jayadratha, whose father performs austerity: 'whoever shall cause my son's head to fall to the ground, his head too shall fall' — thus. Karṇa too, endowed with the infallible power-weapon given by Vāsava, is the son of the Sun, born to an unwed mother, since this is so; therefore the designation is by that very name. Those slain by me, you strike down, as a mere instrumental cause. Do not be distressed on their account; do not make fear. Fight — you will conquer, in the battle, in the fight, Duryodhana and the rest, the rivals, the enemies.