The puruṣa you are referring to is Lord Mahā-Viṣṇu.
Lord Kṛṣṇa and Arjuna go to the abode of Mahā-Viṣṇu. They see him seating on the thousand-hooded serpent Ananta. Lord Kṛṣṇa greeted himself who is in the form of Viṣṇu. Then Lord Viṣṇu [said]
I brought the brāhmaṇa’s sons here because I wanted to see the two of you, My expansions, who have descended to the earth to save the principles of religion. As soon as you finish killing the demons who burden the earth, quickly come back here to Me. 10.89.58
Although all your desires are completely fulfilled, O best of exalted personalities, for the benefit of the people in general you should continue to exemplify religious behavior as the sages Nara and Nārāyaṇa. 10.89.59
Lord Viṣṇu returned the brāhmaṇa’s sons. Lord Kṛṣṇa and Arjuna returned to Dvārakā.
Yes, the puruṣa i.e., Lord Viṣṇu is mentioned in many scriptures.