कथं भीष्ममहं संख्ये द्रोणं च मधुसूदन। इषुभिः प्रतियोत्स्यामि पूजार्हावरिसूदन ॥

kathaṁ bhīṣhmam ahaṁ sankhye droṇaṁ cha madhusūdana iṣhubhiḥ pratiyotsyāmi pūjārhāvari-sūdana

How, O Madhusûdana, shall I attack Bhîshma and Drona with arrows in battle, they who are worthy of reverence, O slayer of foes?

In plain words: Arjuna asks Krishna how he can shoot arrows at Bhīshma, his great-uncle, and Drona, his teacher. These are men he should honor and respect.