Sleep, or the lack of it, is a prevalent theme in Shakespeare's Macbeth.
As Kenneth Muir points out in "Image and Symbol in Macbeth," found in A Norton Critical Edition of the play (254-266), the first mention of the theme of sleep in the play is made by the First Witch:
Sleep shall neither night nor day
Hang upon his penthouse lid. (1.2.20-21)
She curses the Master of a ship, because his wife slights her. After Macbeth and Lady Macbeth assassinate Duncan, they
In the affliction of these terrible dreams
That shake us nightly;... (3.2.19-21)
In contrast, King Duncan, once dead, "sleeps well" (3.2.25). And, says Muir:
An anonymous lord looks forward to the overthrow of the tyrant, when they will be able to sleep in peace. Because of 'a great perturbation in nature' [5.1.8.], Lady Macbeth
is troubled with thick coming fancies
That keep her from her rest. [5.3.39-40]
But the key passage concerning sleep is the one you ask about:
Methought I heard a voice cry "Sleep no more!
Macbeth does murder sleep," the innocent sleep,
Sleep that knits up the raveled sleeve of care,
The death of each day's life, sore labor's bath,
Balm of hurt minds, great nature's second course,
Chief nourisher in life's feast-- (Act 2.2.38-43)
Thus, sleep becomes insomnia, with the dead Duncan the only figure in the play capable of sleeping. Even the drunk, comic Porter's sleep is interrupted, once the deed of assassination is done.