It was the svayamwara competition of Draupadi, where she is expected to choose her husband, both Arjuna and Karna are present.
Arjuna and his brothers, however, are disguised as mendicant Brahmins. They use this false identity in exile because Duryodhana had attempted to kill them using various schemes, including burning the lacquer house – custom built for the Pandavas by Duryodhana – along with the forest while they were sleeping.
So, when many princes and Karna seeking Draupadi as their bride failed to "string a legendary bow" step of the competition, the mendicant Arjuna steps forward and strings it. Karna then objects.
Karna's objection is that the competition is only meant for Kshatriyas, and Brahmins such as "the mendicant who just strung the bow" should not be competing for the hand of Draupadi, a Kshatriya bride. Duryodhana supports him. The gathered Kshatriyas too angrily support Karna, for they against the mixing of varna (here, Brahmin-Kshatriya marriage).
Arjuna maintains his calm, continues to hide his true identity, insists that he is a "Brahmin who fight".
Arjuna's accomplishments and calmness win Draupadi's heart. Draupadi picks Arjuna and awards the garland to him, signify that she chooses to marry the disguised-Brahmin Arjuna.
The varna-based discrimination and verbal insults on Arjuna, for lovely Draupadi's hand, one that Karna initiates at the time of Draupadi's svayambara competition comes back to haunt him many times through angry Bhima and others who remind Karna that he is merely a suta-putra (son of a charioteer).
Draupadi too never likes Karna thereafter.
Arjuna and his brothers, however, are disguised as mendicant Brahmins. They use this false identity in exile because Duryodhana had attempted to kill them using various schemes, including burning the lacquer house – custom built for the Pandavas by Duryodhana – along with the forest while they were sleeping.
So, when many princes and Karna seeking Draupadi as their bride failed to "string a legendary bow" step of the competition, the mendicant Arjuna steps forward and strings it. Karna then objects.
Karna's objection is that the competition is only meant for Kshatriyas, and Brahmins such as "the mendicant who just strung the bow" should not be competing for the hand of Draupadi, a Kshatriya bride. Duryodhana supports him. The gathered Kshatriyas too angrily support Karna, for they against the mixing of varna (here, Brahmin-Kshatriya marriage).
Arjuna maintains his calm, continues to hide his true identity, insists that he is a "Brahmin who fight".
Arjuna's accomplishments and calmness win Draupadi's heart. Draupadi picks Arjuna and awards the garland to him, signify that she chooses to marry the disguised-Brahmin Arjuna.
The varna-based discrimination and verbal insults on Arjuna, for lovely Draupadi's hand, one that Karna initiates at the time of Draupadi's svayambara competition comes back to haunt him many times through angry Bhima and others who remind Karna that he is merely a suta-putra (son of a charioteer).
Draupadi too never likes Karna thereafter.