SB 1.15.7
yat-samsrayad drupada-geham upagatanam
rajñam svayamvara-mukhe smara-durmadanam
tejo hrtam khalu mayabhihatas ca matsyah
sajjikrtena dhanusadhigata ca krsna
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Only by His merciful strength was I able to vanquish all the lusty princes assembled at the palace of King Drupada for the selection of the bridegroom. With my bow and arrow I could pierce the fish target and thereby gain the hand of Draupadi.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Draupadi was the most beautiful daughter of King Drupada, and when she was a young girl almost all the princes desired her hand. But Drupada Maharaja decided to hand over his daughter to Arjuna only and therefore contrived a peculiar way. There was a fish hanging on the inner roof of the house under the protection of a wheel. The condition was that out of the princely order, one must be able to pierce the fish’s eyes through the wheel of protection, and no one would be allowed to look up at the target. On the ground there was a waterpot in which the target and wheel were reflected, and one had to fix his aim towards the target by looking at the trembling water in the pot. Maharaja Drupada well knew that only Arjuna or alternately Karna could successfully carry out the plan. But still he wanted to hand his daughter to Arjuna. And in the assembly of the princely order, when Dhrstadyumna, the brother of Draupadi, introduced all the princes to his grown-up sister, Karna was also present in the game. But Draupadi tactfully avoided Karna as the rival of Arjuna, and she expressed her desires through her brother Dhrstadyumna that she was unable to accept anyone who was less than a ksatriya. The vaisyas and the sudras are less important than the ksatriyas. Karna was known as the son of a carpenter, a sudra. So Draupadi avoided Karna by this plea. When Arjuna, in the dress of a poor brahmana, pierced the difficult target, everyone was astonished, and all of them, especially Karna, offered a stiff fight to Arjuna, but as usual by the grace of Lord Krsna he was able to emerge very successful in the princely fight and thus gain the valuable hand of Krsna, or Draupadi. Arjuna was lamentingly remembering the incident in the absence of the Lord, by whose strength only he was so powerful.