Khandogya-Upanishad: Eighth Prapathaka, Fourth Khanda
1. That Self is a bank, a boundary, so that these worlds may not be confounded. Day and night do not pass that bank, nor old age, death, and grief; neither good nor evil deeds. All evil-doers turn back from it, for the world of Brahman is free from all evil.
2. Therefore he who has crossed that bank, if blind, ceases to be blind; if wounded, ceases to be wounded; if afflicted, ceases to be afflicted. Therefore when that bank has been crossed, night becomes day indeed, for the world of Brahman is lighted up once for all.
3. And that world of Brahman belongs to those only who find it by abstinence—for them there is freedom in all the worlds.