"Be innocent of the knowledge, dearest chuck,
Till thou applaud the deed. Come, seeling night,
Scarf up the tender eye of pityful day,
And with thy bloody and invisible hand
Cancel and tear to pieces that great bond
Which keeps me pale."

No other motive for murder is possible to Shakespeare-Macbeth but fear.

Banquo is murdered, but still Macbeth cries:
"I am cabined, cribbed, confined, bound in
To saucy doubts and fears."
The scene with the ghost of Banquo follows, where-in Macbeth again shows
the nervous imaginative Hamlet nature. His next speech is mere
reflection, and again Hamlet might have framed it:

"the time has been
That when the brains were out the man would die
And there an end": ...

But while fear may be an adequate motive for Banquo's murder, it can
hardly explain the murder of Macduff's wife and children. Shakespeare
feels this, too, and therefore finds other reasons natural enough; but
the first of these reasons, "his own good," is not especially
characteristic of Macbeth, and the second, while perhaps characteristic,
is absurdly inadequate: men don't murder out of tediousness:

"For mine own good
All causes shall give way: I am in blood[1]