Bhagavad Gita

ಅರ್ಜುನ ಉವಾಚ ।
ಕಥಂ ಭೀಷ್ಮಮಹಂ ಸಂಖೇ ದ್ರೋಣಂ ಚ ಮಧುಸೂದನ ।
ಇಷುಭಿಃ ಪ್ರತಿಯೋತ್ಸ್ಯಾಮಿ ಪೂಜಾರ್ಹಾವರಿಸೂದನ ॥೪॥
arjuna uvāca |
kathaṃ bhīṣmamahaṃ saṃkhe droṇaṃ ca madhusūdana |
iṣubhiḥ pratiyotsyāmi pūjārhāvarisūdana ||4||

Gist of the sloka:
Arjuna spoke. O Madhusudhana, how can I kill Bheeshmacharya, Drona who are worthy of worship through my arrows in this battlefield?
Seeing Lord Krishna, having a smiling face and the way Lord replied to him, Arjuna undergoes a [tone] change, in the direction of surrender to Lord.
Arjuna is indicating that Bheeshmacharya is the grand sire of the clan and seen as Raja rishi and whereas Dronacharya is renowned teacher and considered as Maha rishi of the times. Given their exalted status, Arjuna is indicating he cannot kill them in the battle.
Arjuna invokes the name of Madhusudhana. It means among many other, one who has killed the daemon Madhu. Madhu means desires especially physical in nature. Arjuna is trying to say, how come you who have killed such a daemon, now want me to kill such pious gentlemen. Killing pious persons is not the intent of your avatar.