Is there a quote in Shakespeare's Macbeth that means the following?

No, there is no such quote. Macbeth, the man who commits, or is behind the commission of, the murders in the play does so against his better nature. Indeed, his wife has to push him into the murder of Duncan and then does the deed herself. Later Macbeth employs three murderers; he doesn't do the deed himself.

Once embarked upon the fatal course, Macbeth is trapped into acting as though murder would be the solution, but he finds after the first murder, more have to be committed to free himself of the guilt and worry over the first, and then the second killing--of Banquo--is also not an answer. There is a snowball effect. If anything, the play proves the falsity of the idea that murder is the solution. Murder drains the soul out of Macbeth until life itself has no meaning for him.

However, the play is not written like a thesis. It is written as a drama, so you won't find a citation of the kind you want.