The wisdom of tradition.
Proven by science.

The Charaka Samhita devotes half of its Sutrasthana chapter 21 to sleep (nidra) and treats it as governing far more than rest: verse 36 lists "knowledge and ignorance" among the things that depend on sleep, alongside strength, growth, and virility, while verses 46 to 49 warn that unwholesome daytime sleep brings a "delusion of memory and intellect" along with bodily heaviness and fever. Verse 37 goes further, warning that sleep taken out of time, in excess, or not at all "swallows up life and happiness like unto another Night of Destruction." The Sushruta Samhita adds that the self "recollects through the agency of the mind" during sleep, describing dreams as recollections of past deeds, and grades sleep patterns by temperament.

What the science saysModern research backs the specific claim that sleep and memory are linked; cognition really does depend on adequate sleep, but through hippocampal and cortical memory consolidation during slow-wave and REM sleep rather than through the textual framework of tamas or humoral balance.