Śrīmad-Bhāgavatam · Text 12.6.50
Who is speaking and story frame
ऋगथर्वयजु:साम्नां राशीरुद्धृत्य वर्गश: ।
चतस्र: संहिताश्चक्रे मन्त्रैर्मणिगणा इव ॥ ५० ॥
ṛg-atharva-yajuḥ-sāmnāṁ
rāśīr uddhṛtya vargaśaḥ
catasraḥ saṁhitāś cakre
mantrair maṇi-gaṇā iva
Śrīla Vyāsadeva separated the mantras of the Ṛg, Atharva, Yajur and Sāma Vedas into four divisions, just as one sorts out a mixed collection of jewels into piles. Thus he composed four distinct Vedic literatures.
Read the purport on Vedabase.ioFrom Canto 10, chapter 14 onward, the translation and purports were completed by Śrīla Prabhupāda's disciples after his departure, and published by the Bhaktivedanta Book Trust.