Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 5

Sanskrit:

उत्थापनैरुन्नयनैश्चालनै: स्थापनैरपि । परस्परं जिगीषन्तावपचक्रतुरात्मन: ॥ ५ ॥

ITRANS:

utthāpanair unnayanaiścālanaiḥ sthāpanair apiparasparaṁ jigīṣantāvapacakratur ātmanaḥ

Translation:

Forcefully lifting and carrying each other, pushing each other away and holding each other down, the fighters hurt even their own bodies in their great eagerness for victory.

Purport:

Śrīla Jīva Gosvāmī explains that although Kṛṣṇa and Balarāma did not, of course, harm Themselves, it appeared that way to Cāṇūra, Muṣṭika and others of mundane vision. In other words, the Lords were fully absorbed in the pastime of being wrestlers.