Macbeth relationship with the witches

If it were not for the witches, I don't think Macbeth would have killed Duncan. Macbeth was a trustworthy and honest man before he came in contact with the witches, he fought for his country and king. The tempted Macbeth with their story of fame and riches. After seeing the first part of their story come true Macbeth seemed to be interested in the next part about him becoming king. Until that point Macbeth couldn't have imagined himself becoming king; but the witches planted that seed in his mind and Macbeth eventually would become obsessed with the witches foresight's and base his actions on them.