SB 5.14.20
sa eva punar nidrajagara-grhito ’ndhe tamasi magnah sunyaranya iva sete nanyat-kiñcana veda sava
ivapaviddhah.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Sukadeva Gosvami continued speaking to Maharaja Pariksit: My dear King, sleep is exactly like a python. Those who wander in the forest of material life are always devoured by the python of sleep. Being bitten by this python, they always remain in the darkness of ignorance. They are like dead bodies thrown in a distant forest. Thus the conditioned souls cannot understand what is going on in life.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Material life means being fully absorbed in eating, sleeping, mating and defending. Out of these, sleep is taken very seriously. While asleep, one completely forgets the object of life and what to do. For spiritual realization, one should try to avoid sleep as much as possible. The Gosvamis of Vrndavana practically did not sleep at all. Of course, they slept some, for the body requires sleep, but they slept only about two hours, and sometimes not even that. They always engaged in spiritual cultivation. Nidrahara-viharakadi-vijitau. Following in the footsteps of the Gosvamis, we should try to reduce sleeping, eating, mating and defending.