Mbh 7.197.4b

Although in speaking of Aswatthaman’s death thou hadst added the word elephant, yet thy answer to the preceptor was, after all, an untruth in the garb of truth. Thus told by thee, the puissant Drona laid aside his weapons and, as thou sawest, became indifferent (to everything), exceedingly agitated, and almost deprived of his senses. It was even a disciple who, abandoning all morality, thus slew his own preceptor, full of affection for his son, while, indeed, that preceptor was filled with grief and unwilling to fight. Having caused him, who had laid his weapons to be unrighteously slain, protect the son of Prishata if thou canst, with all thy counsellors. All of us, uniting together, shall not be able to protect Prishata’s son today, who will be assailed by the preceptor’s son in wrath and grief. That superhuman being who is in that habit of displaying his friendship for all creatures, that hero, hearing of the seizure of his sire’s locks, will certainly consume us all in battle today. Although I cried repeatedly at the top of my voice for saving the preceptor’s life, yet, disregarding my cries and abandoning mortality, a disciple took the life of that preceptor. All of us have passed the greater part of our lives. The days that remain to us are limited. This exceedingly unrighteous act that we have perpetrated has stained that remnant. In consequence of the affection he bore to us, he was a sire unto us. According to the dictates of the scriptures also, he was a sire unto us. Yet he, that preceptor of ours, has been slain by us for the sake of short-lived sovereignty. Dhritarashtra, O king, had given unto Bhishma and Drona the whole earth, and what was still more valuable, all his children. Though honoured by our foe thus, and though he had obtained such wealth from him, the preceptor still loved us as his own children. Of unfading energy and prowess, the preceptor has been slain, only because, induced by thy words he had laid aside his weapons.