Bg 2.4

arjuna uvaca
katham bhismam aham sankhye
dronam ca madhusudana
isubhih pratiyotsyami
pujarhav ari-sudana

Word for word: 
arjunah uvaca — Arjuna said; katham — how; bhismam — Bhisma; aham — I; sankhye — in the fight; dronam — Drona; ca — also; madhu-sudana — O killer of Madhu; isubhih — with arrows; pratiyotsyami — shall counterattack; puja-arhau — those who are worshipable; ari-sudana — O killer of the enemies.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Arjuna said: O killer of enemies, O killer of Madhu, how can I counterattack with arrows in battle men like Bhisma and Drona, who are worthy of my worship?

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Respectable superiors like Bhisma the grandfather and Dronacarya the teacher are always worshipable. Even if they attack, they should not be counterattacked. It is general etiquette that superiors are not to be offered even a verbal fight. Even if they are sometimes harsh in behavior, they should not be harshly treated. Then, how is it possible for Arjuna to counterattack them? Would Krishna ever attack His own grandfather, Ugrasena, or His teacher, Sandipani Muni? These were some of the arguments offered by Arjuna to Krishna.