न्यस्तशस्त्रमधर्मेण घातयित्वा गुरुं भवान्
nyastaśastram adharmeṇa ghātayitvā guruṃ bhavān
Having slain the teacher by unrighteous means when he had laid down his weapons, you would be acting against dharma.
अजुन उवाच