Bhagavad Gita 15.1

भगवान श्रीउवाच |
ऊर्ध्वमूलमध:शाखमश्वत्थं प्राहुरव्ययम् |
छंदंसि यस्य पूर्णानि यस्तं वेद स वेदवित

Translation

The Supreme Divine Personality said: They speak of an eternal aśhvatth tree with its roots above and branches below. Its leaves are the Vedic hymns, and one who knows the secret of this tree is the knower of the Vedas.