You [Prahlada Maharaja] once went to the Naimisa Forest to have darsana of Narayana, who is known as "the Lord in yellow dress." While on the road you satisfied the Lord in combat, and He told you, "Yes, I am always conquered by you!"
This incident is recounted in a number of scriptures, including the Vamana Purana (7). Once Prahlada took a trip to Naimisaranya to see Lord Pitavasa, the beautiful form of the Supreme Lord. While traveling on the road he met a strange person, who was dressed like an austere renunciant but was carrying a warrior's bow and arrows. Prahlada assumed from this person's contradictory attire that he must be some hypocrite abusing the true principles of religion. Therefore Prahlada started a fight with the
sannyasi, vowing "I swear I shall defeat you!" But even after several days of dueling, Prahlada could not subdue this adversary. Early one morning before resuming the battle, Prahlada worshiped his personal Deity. He then saw his opponent standing nearby, wearing the same garland he had just offered the Deity. Prahlada suddenly recognized that the stranger was Lord Pitavasa, Narayana Himself. Thereupon, offering prayers to that opponent with all the competence at his command, Prahlada tried to
satisfy Him. In response, the Lord touched him with His lotus hand, which relieved Prahlada from the fatigue of fighting and from all anxiety. Prahlada asked Lord Pitavasa what to do about having transgressed the duty of a ksatriya by having made a promise -- namely to defeat his opponent -- and not having fulfilled it. The Lord, fully satisfied by the sport of fighting with Prahlada, told him, "But I am always defeated by you!"
Brhad Bhagavatamrta 1.4.11 by Srila Sanatana Gosvami