Bhagavad Gita · 15.1

श्रीभगवानुवाचऊर्ध्वमूलमधःशाखमश्वत्थं प्राहुरव्ययम्।छन्दांसि यस्य पर्णानि यस्तं वेद स वेदवित्॥

śhrī bhagavān uvācha ūrdhva-mūlam adhaḥ-śhākham aśhvatthaṁ prāhur avyayam chhandāṁsi yasya parṇāni yas taṁ veda sa veda-vit

The Supreme Lord said: They speak of the imperishable ashvattha tree, with its roots above and branches below, whose leaves are the Vedic hymns. One who knows this tree truly knows the Vedas.

— Bhagavad Gita 15.1

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)