Continuing to depict duality, the two opposites, that originates from one existing in the supreme unity, the Upanishad says: Ahoratro Vai Prajapati.
It says day and night is verily lords of creation. The day indeed is life and night is matter. Those who have intercourse by day, spill their life (prana) and those who have intercourse by night are chaste indeed. This is interesting.
Praanam vaa ete praskandanti. Ye divaa ratyaa sanyujyante brahmacharyamev tadyadraatrau ratyaa sanyujyante.
It means, Brahmacharya is not complete abstinence from sex, but control of sex. The Prasnopanishad declares that those who have sexual intercourse by day are not chaste because they spill their prana. Those who have sexual intercourse by night are chaste indeed. It means there must be a certain control of energies, not complete abstinence, because the Upanishads, despite their exultation of celibacy, recognises the value of married life. Most of the Rishis were married.
From here, the Upanishad proceeds saying:
Annam Vai Prajapatihi
Food is indeed the lord of creation. From food comes the vital material required for reproduction and from this, creatures are born. The Upanishad talks of the exalted, untouchable, unreachable spiritual being and then, brings it down to the ordinary level of day-to-day things, thus blending them. While admitting that the Supreme Brahman is absolute, it also says that the Supreme Brahman, in this case, as far as existence is concerned, manifests itself as food.