The line you ask about in Shakespeare's Macbeth is from the famous "Tomorrow" speech, spoken by Macbeth. Here's the line with some context:
She should have died hereafter [at some better time; later, rather than sooner];
There would have been a time for such a word [the word he just received that his wife was dead].
Tomorrow, and tomorrow, and tomorrow
Creeps in this petty pace from day to day
To the last syllable of recorded time,
And all our yesterdays have lighted fools
The way to dusty death.... (Act 5.5.17-23)
The repetition of tomorrow suggests tedium, endless repetition, and tomorrow creeps in slowly from one day to the next, always, and it is just as useless as all of the yesterdays.
Macbeth slips into nihilism, here, the belief that nothing matters, and nothing makes any difference. His wife's death is the trigger that moves him to hopelessness. All the yesterdays lead one only to the dusty grave. And between the beginning and the end what happens is irrelevant.
Interestingly, this scene is one of several that shows Macbeth figuratively jumping back and forth between emotionally feeling he is invincible because of the witches' predictions, and rationally knowing the predictions are too good to be true and that he is doomed.