The Mukhya Upaniṣads

Īśa · The Whole World in the Light of the Self

Mantra 3

असुर्या नाम ते लोका अन्धेन तमसाऽऽवृताः ।तांस्ते प्रेत्याभिगच्छन्ति ये के चात्महनो जनाः ॥ ३ ॥

In plain words

Sunless indeed are those worlds, covered by blinding darkness. To them, after death, go those people who slay the Self, as it were.