I am not sure your question, but the witches had 3 prophecy for mcbeth.
1st- he will be thane of cawdor, which I believe he is awarded for his bravery in battle. Awarded by king duncan (don't quote me on that I am not sure, its been a while)
2nd- Mcbeth shall be king- Which he is after he kills duncan
3nd -none of woman born/Shall harm Macbeth (I believe this is what you are looking for) He doesn't think that Macduff can harm him, because everyone must be born of from a women, but macduff was born via c-section. So he killed macbeth, macbeth was will to go in battle with macduff because he think no one can beat him. So it encourages macbeth to fight macduff.