Once, Arjun (when Pandavas were exiled) was on his pilgrimage. He visited many pilgrimages. On such occasions, Arjun went to Rameshwaram temple to see the Shivalinga that was made by Lord Rama. Before setting off to Lanka, Lord Rama worshiped Lord Shiva seeking His blessing for his victory over the Danava king- Ravana! After seeking the blessing from Shivalinga (Lord Shiva) Arjun proceeded towards the ocean to behold the amazing Rama Setu bridge that he heard so much! He gazed at the bridge for a long time. His heart was filled with wonder and he thought, ‘Lord Rama was known as a God! As Krishna told me he was the best archer! If he wished, he could have constructed an arrow bridge by himself! Why did he take help from the monkeys and even a squirrel? What was so difficult for him?’ He mused over his query for a long time but couldn't get the answer!’
While Arjun was still engaged in beholding the bridge, a monkey approached him. He asked, ‘Why are you looking at the bridge for such a long time?’
Arjun then revealed his curiosity to know the reason for the monkeys’ contribution to the Rama Setu bridge while Rama himself could make an arrow bridge across the ocean.
Hearing the words of Arjun, the monkey laughed aloud and then said, ‘Arrow bridge? Do you think that an arrow bridge can withstand the strength of Neela, Sugriva, and Angada? Even the arrow bridge can't hold my weight what about them? If I step on it, it will collapse!’
The monkey’s satirical statement was unbearable for Arjun. He looked at his face and said, ‘Do you know who I am? Do you have any idea about my prowess? I am the disciple of Dronacharya and son of Pandu. I can make an arrow bridge that can hold your weight! Let us take it as a challenge. And if the bridge collapses then I will accept self-immolation entering into fire!’
The monkey agreed to his challenge. Thus, Arjun took his Gandiva bow and built a sturdy bridge. While Arjun was busy with his work, the monkey was continuously chanting the name -Shri Ram...Shri Ram. After finishing the work Arjun asked the monkey to cross it. But instead of putting his full weight, the monkey simply put his tail and the bridge collapsed. Arjun was stunned and attempted a second trial. Barely did the monkey take a few steps, and once again the bridge collapsed.
Arjun felt ashamed of losing the challenge to a mere old monkey! He thought his archery was no more useful to him. As per the challenge he prepared a pyre to kill himself. Just at that very moment a young Brahmana who was passing by saw Arjun ready for self-immolation. He stopped him and asked the reason. Hearing about the challenge, the Brahmana asked if there was any third person who could witness or judge. Both Hanuman and Arjun replied there was none.
Then the young Brahmana said, ‘Huh! Don't you know that there should be a witness when anyone takes a challenge? If there is none, then it's not a challenge. Now one more time you construct the bridge and I will be the witness!’
Once again Arjun tried but this time his mind was covered with fear. He thought of Lord Krishna and prayed to him with heart to save his prestige. With full devotion and confidence, Arjun built the arrow bridge. The monkey was confident that as Arjun failed twice, this time also he would fail. Thus the monkey stepped on the bridge. But lo, behold! Nothing had happened to the bridge! He started jumping, hopping, stamping but the bridge remained as it was! He tried with all his might and strength but the bridge didn't collapse! Both Arjun and the monkey were startled! Getting furious, the monkey took his form. At last, the monkey revealed his form! He was no other than Shri Hanuman ji!
Looking at the divine form of Lord Hanuman, Arjun was thrilled and felt guilty about making him his challenger! He bowed his head with reverence on Shri Hanuman’s feet. Hanuman himself was surprised to see the miracle! He couldn't believe that after applying all his strength and might how could the bridge sustained? He looked at the Brahmana. But the Brahmana was at nowhere! Out of anxiety when he looked under the bridge he saw the Brahmana. He was stunned at the sight! He was none other than Lord Vishnu who supported the bridge on his shoulders.
Both Arjun and Hanuman ji became speechless! They prostrated on His feet. They sought the Lord’s forgiveness. With a smiling face, Lord Vishnu said, ‘O Arjun! O Hanuman! I am Rama and I am Krishna! Pride and ego do no good to humans! At one point, both of your minds are filled with ego and pride. O Arjun, you are as dear to me as Hanuman is!’
When Hanuman felt sad that he made his Master shouldered his weight! Lord Vishnu consoled him with sweet words saying that he was indebted to him in Treteya Yuga! He loves to serve His devotees to reciprocate their love and devotion! Lord Hanuman promised Lord Vishnu that since he had driven Arjun to sacrifice his life, he would help him throughout the great battle to win over his enemies! Thus, Hanuman was always present in the banner of Arjun. It was called as ‘Kapidhwaja’!