Khandogya-Upanishad: Eighth Prapathaka, Fifteenth Khanda

1. Brahma (Hiranyagarbha or Paramesvara) told this to Pragâpati (Kasyapa), Pragâpati to Manu (his son), Manu to mankind. He who has learnt the Veda from a family of teachers, according to the sacred rule, in the leisure time left from the duties to be performed for the Guru, who, after receiving his discharge, has settled in his own house, keeping up the memory of what he has learnt by repeating it regularly in some sacred spot, who has begotten virtuous sons, and concentrated all his senses on the Self, never giving pain to any creature, except at the tirthas (sacrifices, &c.), he who behaves thus all his life, reaches the world of Brahman, and does not return, yea, he does not return.