SB 6.5.19

kāla-cakraṁ bhrami tīkṣṇaṁ
 sarvaṁ niṣkarṣayaj jagat
svatantram abudhasyeha
 kim asat-karmabhir bhavet
Synonyms: 
kāla-cakram — the wheel of eternal time; bhrami — revolving automatically; tīkṣṇam — very sharp; sarvam — all; niṣkarṣayat — driving; jagat — the world; sva-tantram — independent, not caring for the so-called scientists and philosophers; abudhasya — of one who does not know (this principle of time); iha — in this material world; kim asat-karmabhiḥ bhavet — what is the use of engaging in temporary fruitive activities.
Translation: 
[Nārada Muni had spoken of a physical object made of sharp blades and thunderbolts. The Haryaśvas understood this allegory as follows.] Eternal time moves very sharply, as if made of razors and thunderbolts. Uninterrupted and fully independent, it drives the activities of the entire world. If one does not try to study the eternal element of time, what benefit can he derive from performing temporary material activities?
Purport: 

This verse explains the words kṣaura-pavyaṁ svayaṁ bhrami, which especially refer to the orbit of eternal time. It is said that time and tide wait for no man. According to the moral instructions of the great politician Cāṇakya Paṇḍita:

āyuṣaḥ kṣaṇa eko ’pi
 na labhyaḥ svarṇa-koṭibhiḥ
na cen nirarthakaṁ nītiḥ
 kā ca hānis tato ’dhikā

Even a moment of one’s lifetime could not be returned in exchange for millions of dollars. Therefore one should consider how much loss one suffers if he wastes even a moment of his life for nothing. Living like an animal, not understanding the goal of life, one foolishly thinks that there is no eternity and that his life span of fifty, sixty, or, at the most, one hundred years, is everything. This is the greatest foolishness. Time is eternal, and in the material world one passes through different phases of his eternal life. Time is compared herein to a sharp razor. A razor is meant to shave the hair from one’s face, but if not carefully handled, the razor will cause disaster. One is advised not to create a disaster by misusing his lifetime. One should be extremely careful to utilize the span of his life for spiritual realization, or Kṛṣṇa consciousness.