I will relate to you the reason here of briefly and argumentatively. As we strictly adhere to our own duties, we are not afraid of death.
कारणं वः प्रवक्ष्यामि हेतुयोगसमासतः। सत्यमेवाभिजानीमो नानृते कुर्महे मनः। स्वधर्ममनुतिष्ठामस्तस्मान्मृत्युभयं न नः॥