As confirmed in the Viṣṇu Purāṇa:

atharva-vedaḿ sa muniḥ

sumantur amita-dyutiḥ

śiṣyam adhyāpayām āsa

kabandhaḿ so 'pi ca dvidhā

kṛtvā tu vedadarśāya

tathā pathyāya dattavān

"That sage Sumantu, whose brilliance was immeasurable, taught the Atharva Veda to his disciple Kabandha. Kabandha in turn divided it into two parts and passed them down to Vedadarśa and Pathya."