BṚHADĀRAṆYAKA UPANISHAD · 4.4.10

अन्धं तमः प्रविशन्ति ये ऽविद्याम् उपासते ।
ततो भूय इव ते तमो य उ विद्यायां रताः ॥

andhaṃ tamaḥ praviśanti ye ’vidyām upāsate ।
tato bhūya iva te tamo ya u vidyāyāṃ ratāḥ ॥

'All who worship what is not knowledge (avidyâ) enter into blind darkness: those who delight in knowledge, enter, as it were, into greater darkness.

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)