Yoga Sūtra Chapter One verse 10

अभावप्रत्ययालम्बना तमोवृत्तिर्निद्र ॥१०॥

abhāva-pratyaya-ālambanā tamaḥ vṛttiḥ nidrā ||10||

Deep sleep is the fluctuation of obscuring,
supporting a non-appearance of psychic activity.

abhāva - non-appearance, non-existence, absencepratyaya - psychic activity; cause; conception, assumption, notion, idea;ālambana - supporting, resting ontamas - obscuringvṛtti - fluctuation; modification; turned; set in motion, course of action, behaviour, movement; activity, function; professionnidrā - deep sleep

Commentaries and Reflections

Commentary by Paul Harvey:

Deep sleep is the obscuring of the fluctuations,
resulting in the non-appearance of mental activity.

Inspirational Quote

“Happiness, it seems to me, consists of two things: first, in being where you belong, and second -- and best -- in comfortably going through everyday life, that is, having had a good night's sleep and not being hurt by new shoes....” Theodor Fontane