Caitanya-caritāmṛta 5.8
śrī-balarāma gosāñi mūla-saṅkarṣaṇa pañca-rūpa dhari’ karena kṛṣṇera sevana
[shree-balaraama gosaani moola-sankarshana pancha-roopa dhari’ karena krishnera sevana]
Blended reading (Sanskrit + English inline)
śrī-balarāma gosāñi mūla-saṅkarṣaṇa pañca-rūpa dhari’ karena kṛṣṇera sevana
Lord Balarāma is the original Saṅkarṣaṇa. He assumes five other forms to serve Lord Kṛṣṇa.
My note
Source: vedabase.io