SB 1.4.20
ऋग्यजु:सामाथर्वाख्या वेदाश्चत्वार उद्‍धृता: ।
इतिहासपुराणं च पञ्चमो वेद उच्यते ॥ २० ॥
ṛg-yajuḥ-sāmātharvākhyā
vedāś catvāra uddhṛtāḥ
itihāsa-purāṇaṁ ca
pañcamo veda ucyate
SYNONYMS

ṛg-yajuḥ-sāma-atharva-ākhyāḥ—the names of the four Vedas; vedāḥ—the Vedas; catvāraḥ—four; uddhṛtāḥ—made into separate parts; itihāsa—historical records (Mahābhārata); purāṇam ca—and the Purāṇas; pañcamaḥ—the fifth; vedaḥ—the original source of knowledge; ucyate—is said to be.

TRANSLATION

The four divisions of the original sources of knowledge [the Vedas] were made separately. But the historical facts and authentic stories mentioned in the Purāṇas are called the fifth Veda.