Bhagavad Gita · 2.46

यावानर्थ उदपाने सर्वतः सम्प्लुतोदके।तावान्सर्वेषु वेदेषु ब्राह्मणस्य विजानतः॥

yāvān artha udapāne sarvataḥ samplutodake tāvān sarveṣhu vedeṣhu brāhmaṇasya vijānataḥ

To the enlightened Brahmin, all the Vedas are of as much use as a small well when there is a flood of water everywhere.

— Bhagavad Gita 2.46

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