Which lines in the play show how Banquo is a character foil to Macbeth?Any quotations or general areas that I could find some good examples of it would be great.
The fates of Macbeth and Banquo are inextricably linked, and Banquo is clearly the foil for Macbeth’s foray into following the dark forces of evil.
In Act 1 Scene iii when the witches give the prophesy to Macbeth, which is the prompt for him to embark on the fatal path to be king, Banquo is at his side. Banquo also receives predictions from the witches:
Lesser than Macbeth, and greater.
Not so happy, yet much happier.
Thou shalt get kings, though thou be none.(70)
So all hail, Macbeth and Banquo!
However, Banquo chooses a different pathway; that he will see out his own future without action to advance the witches’ predictions. This is, of course, ultimately fatal for him. Macbeth’s decision to act upon what he has been told also seals his downfall. The witches prophesies destroy both of them, Macbeth the follower of the evil and Banquo the honest soldier.
Yes, and later in Act 1, Scene 3, after Macbeth learns that part of the witches' prophecy has come true, that he has, indeed, been named the Thane of Cawdor, he says to Banquo:
...Do you not hope your children shall be kings,
When those that gave the Thane of Cawdor to me
Promised no less to them?
Banquo's answer is a cautious one. He's not so sure that the witches "gave" anyone anything. A prediction or a prophesy may only be a suggestion about the future, not an outright gift. So Banquo warns:
That, trusted home,
Might yet enkindle you unto the crown,
Besides the Thane of Cawdor. But ’tis strange;
And oftentimes, to win us to our harm,
The instruments of darkness tell us truths,
Win us with honest trifles, to betray's
In deepest consequence
To Macbeth's wide-eyed amazement and belief, Banquo brings wariness, common sense and a cool head.
Later in the play, Banquo serves as the ultimate foil to Macbeth, when in Act 3, Scene 4, Banquo's ghost comes to taunt Macbeth at the formal dinner party; the bloody ghost points to Macbeth, exposing a horrified Macbeth to his own guilt.