This quote shows how responsible Banquo really is. His best friend is receiving nice titles and lands, but he is looking at the bigger picture. He can emotionally feel that Macbeth is going about this success the wrong way without having evidence. Banquo is truly smart and bold in this scene. This shows a humble side to Banquo
This quote adds to the entire play because it shows how Macbeth actually has lost his character. At the beginning of the play he was known as noble and wise, but now he is a monster. "Played'st most foully for't", to me this means that Macbeth has let the sudden success get to his head. He is no longer the same respectable man that he once was.