Spender, Stephen. "Time, Violence, and Macbeth."
The Penguin New Writing 3 (February 1941): 115-126.
Thesis: The general topic of this rambling essay is time-obsession in the English literature which was modern at the time the essay was written — when England stood alone against Hitler. The six-page section on Macbeth isn't strongly connected to the rest of essay, but it is valuable for its insights about Shakespeare's play.

Spender writes,

In the minds of Macbeth and Lady Macbeth there are, after the prophetic meeting with the weird sisters, three kinds of time: the time before the murder, the time of the murder of Duncan, and the enjoyable time afterwards when they reap the fruits of the murder. Their problem is to keep these three times separate and not to allow them to affect each other.  (121).
This is a problem which they do not solve. "The Sleepwalking scene is a shocking revelaion which shows that the moment when [Lady Macbeth] smeared the faces of the grooms has died no more for her than has the murder for Macbeth" (124). As for Macbeth,
The horror of not being able to live down his deeds is symbolized by the appearance of Banquo's ghost. Macbeth looks back on a time when the past was really past the present present:
                     'The time has been
That, when the brains were out, the man would die,
And there an end.'
     There is no end within the control of Macbeth. In the fourth act, we even have a feeling that everything has stopped. The play seems to spread out, burning up and destroying a wider and wider area, without moving forward.
     "To-morrow, and to-morrow and to-morrow' is not merely the speech of a disillusioned tyrant destroyed by the horror which he has himself created; it is a profound irony, coming from Macbeth's mouth, because he of all people ought to have been able to make to-morrow different from to-day and yesterday. But all his violence has done is to create a deathly sameness.  (124-125)

Bottom Line: Worthwhile.