Bhagavad Gita: Chapter 1, Verse 20

अथ व्यवस्थितान्दृष्ट्वा धार्तराष्ट्रान् कपिध्वज: |
प्रवृत्ते शस्त्रसम्पाते धनुरुद्यम्य पाण्डव: || 20||
हृषीकेशं तदा वाक्यमिदमाह महीपते |

atha vyavasthitān dṛiṣhṭvā dhārtarāṣhṭrān kapi-dhwajaḥ
pravṛitte śhastra-sampāte dhanurudyamya pāṇḍavaḥ
hṛiṣhīkeśhaṁ tadā vākyam idam āha mahī-pate

athathereupon; vyavasthitānarrayed; dṛiṣhṭvāseeing; dhārtarāṣhṭrānDhritarashtra’s sons; kapi-dwajaḥthe Monkey Bannered; pravṛitteabout to commence; śhastra-sampāteto use the weapons; dhanuḥbow; udyamyataking up; pāṇḍavaḥArjun, the son of Pandu; hṛiṣhīkeśhamto Shree Krishna; tadāat that time; vākyamwords; idamthese; āhasaid; mahī-pateKing

Translation

BG 1.20: At that time, the son of Pandu, Arjun, who had the insignia of Hanuman on the flag of his chariot, took up his bow. Seeing your sons arrayed against him, O King, Arjun then spoke the following words to Shree Krishna.

Commentary

Arjun is called by the name Kapi Dhwaj, denoting the presence of the powerful Hanuman on his chariot. There is a story behind this. Arjun once became proud of his skill in archery, and told Shree Krishna that he could not understand why, in the time of Lord Ram, the monkeys labored so much to make the bridge from India to Lanka. Had he been there, he would have made a bridge of arrows. Shree Krishna asked him to demonstrate. Arjun made the bridge by releasing a shower of arrows. Shree Krishna called Hanuman to come and test the bridge. When the great Hanuman began walking on it, the bridge started crumbling. Arjun realized that his bridge of arrows would never have been able to uphold the weight of the vast army of Lord Ram, and apologized for his mistake. Hanuman then taught Arjun the lesson to never become proud of his skills. He benevolently gave the boon to Arjun that he would sit on his chariot during the battle of Mahabharat. Therefore, Arjun’s chariot carried the insignia of Hanuman on its flag, from which he got the name “Kapi Dhwaj,” or the “Monkey Bannered.”