Shakespeare's Macbeth, Act V Scene 5

Macbeth. She should have died hereafter;
There would have been a time for such a word.
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. Out, out, brief candle!
Life's but a walking shadow, a poor player
That struts and frets his hour upon the stage
And then is heard no more. It is a tale
Told by an idiot, full of sound and fury,
Signifying nothing.l

What does the phrase "brief candle" refer to?

Death
Fools
Pace
Life