“If it were done when ‘tis done, then ‘twere
It were done quickly: if thy assassination
Could trammel up the consequence, and catch
With his surcrease success; that but this blow
Might be the be-all and the end-all.” I, vii, 1-5.
In this phrase, MacBeth is unsure if he really wants to go through
with the act of killing the king. With repeating the 'C' sound at the begining of the word, he is stalling time, hoping
that those around him, or perhaps even himself will get confused.