MUṆḌAKA UPANISHAD · 1.1.5

तत्रापरा ऋग्वेदो यजुर्वेदः सामवेदोऽथर्ववेदः
शिक्षा कल्पो व्याकरणं निरुक्तं छन्दो ज्योतिषमिति ।
अथ परा यया तदक्षरमधिगम्यते ॥ ५॥

tatrāparā ṛgvedo yajurvedaḥ sāmavedo’tharvavedaḥ
śikṣā kalpo vyākaraṇaṃ niruktaṃ chando jyotiṣamiti ।
atha parā yayā tadakṣaramadhigamyate ॥ 5॥

Of which the lower, the Rig Veda and the Yajur Veda and the Sama Veda and the Atharva Veda, chanting, ritual, grammar, etymological interpretation, and prosody and astronomy. And then the higher by which is known the Immutable.

Sri Aurobindo · CWSA 18, p. 132