When Ross and Angus, entering, announce to Macbeth that he has been made Thane of Cawdor, Banquo exclaims, aside, to himself or Macbeth, ’What! can the devil speak true?’ He now believes that the Witches were real beings and the ‘instruments of darkness.’  When Macbeth, turning to him, whispers,

Do you not hope your children shall be kings,
When those that gave the Thane of Cawdor to me
Promised no less to them?

he draws with the boldness of innocence the inference which is really occupying Macbeth, and answers,

That, trusted home,
Might yet enkindle you unto the crown
Besides the thane of Cawdor.

Here he still speaks, I think, in a free, off-hand, even jesting,[234] manner (’enkindle’ meaning merely ’excite you to hope for’).  But then, possibly from noticing something in Macbeth’s face, he becomes graver, and goes on, with a significant ‘but,’

                     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.

He afterwards observes for the second time that his partner is ‘rapt’; but he explains his abstraction naturally and sincerely by referring to the surprise of his new honours; and at the close of the scene, when Macbeth proposes that they shall discuss the predictions together at some later time, he answers in the cheerful, rather bluff manner, which he has used almost throughout, ‘Very gladly.’  Nor was there any reason why Macbeth’s rejoinder, ‘Till then, enough,’ should excite misgivings in him, though it implied a request for silence, and though the whole behaviour of his partner during the scene must have looked very suspicious to him when the prediction of the crown was made good through the murder of Duncan.

In the next scene Macbeth and Banquo join the King, who welcomes them both with the kindest expressions of gratitude and with promises of favours to come.  Macbeth has indeed already received a noble reward.  Banquo, who is said by the King to have ‘no less deserved,’ receives as yet mere thanks.  His brief and frank acknowledgment is contrasted with Macbeth’s laboured rhetoric; and, as Macbeth goes out, Banquo turns with hearty praises of him to the King.

And when next we see him, approaching Macbeth’s castle in company with Duncan, there is still no sign of change.  Indeed he gains on us.  It is he who speaks the beautiful lines,

                        This guest of summer,
     The temple-haunting martlet, does approve,
     By his loved mansionry, that the heaven’s breath
     Smells wooingly here:  no jutty, frieze,
     Buttress, nor coign of vantage, but this bird
     Hath made his pendent bed and procreant cradle: 
     Where they most breed and haunt, I have observed,
     The air is delicate;