Bhagavad Gita: Chapter 1, Verse 3

पश्यैतां पाण्डुपुत्राणामाचार्य महतीं चमूम् ।
व्यूढां द्रुपदपुत्रेण तव शिष्येण धीमता ।। 3।।

paśhyaitāṁ pāṇḍu-putrāṇām āchārya mahatīṁ chamūm
vyūḍhāṁ drupada-putreṇa tava śhiṣhyeṇa dhīmatā

paśhyabehold; etāmthis; pāṇḍu-putrāṇāmof the sons of Pandu; āchāryarespected teacher; mahatīmmighty; chamūmarmy; vyūḍhāmarrayed in a military formation; drupada-putreṇason of Drupad, Dhrishtadyumna; tavaby your; śhiṣhyeṇadisciple; dhī-matāintelligent


BG 1.3: Duryodhan said: Respected teacher! Behold the mighty army of the sons of Pandu, so expertly arrayed for battle by your own gifted disciple, the son of Drupad.


Duryodhan diplomatically pointed to his military preceptor, Dronacharya, the mistake committed by him in the past.  Dronacharya had once had a political quarrel with King Drupad.  Angered by the quarrel, Drupad performed a sacrifice, and received a boon to beget a son who would be able to kill Dronacharya.  As a result of this boon, Dhrishtadyumna was born to him. 

Although Dronacharya knew the purpose of Dhrishtadyumna’s birth, yet out of his large-heartedness, when Dhrishtadyumna was entrusted to him for military education, he did not hesitate to impart all his knowledge to him.  Now, in the battle, Dhrishtadyumna had taken the side of the Pandavas as the commander-in-chief of their army, and he was the one who had arranged their military phalanx.  Duryodhan thus hinted to his teacher that his lenience in the past had gotten them into the present trouble, and that he should not display any further lenience in fighting the Pandavas now.