Bg 2.4

arjuna uvāca
kathaṁ bhīṣmam ahaṁ saṅkhye
droṇaṁ ca madhusūdana
iṣubhiḥ pratiyotsyāmi
pūjārhāv ari-sūdana
Synonyms: 
arjunaḥ uvāca — Arjuna said; katham — how; bhīṣmam — Bhīṣma; aham — I; saṅkhye — in the fight; droṇam — Droṇa; ca — also; madhu-sūdana — O killer of Madhu; iṣubhiḥ — with arrows; pratiyotsyāmi — shall counterattack; pūjā-arhau — those who are worshipable; ari-sūdana — O killer of the enemies.
Translation: 
Arjuna said: O killer of enemies, O killer of Madhu, how can I counterattack with arrows in battle men like Bhīṣma and Droṇa, who are worthy of my worship?
Purport: 

Respectable superiors like Bhīṣma the grandfather and Droṇācārya 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 Kṛṣṇa ever attack His own grandfather, Ugrasena, or His teacher, Sāndīpani Muni? These were some of the arguments offered by Arjuna to Kṛṣṇa.