Any textual evidence from Shakespeare's Macbeth regarding Macbeth's oath to kill the king?

Question

In act 1, scene 7, Lady Macbeth encourages Macbeth to keep his promise and kill king Duncan, but is there any textual evidence from the play regarding his earlier oath to kill the king?

Here, for example, Lady Macbeth says that if she had promised to kill her own child, like Macbeth did in the case of killing the king, she certainly would have done so!

I have given suck, and know
How tender 'tis to love the babe that milks me:
I would, while it was smiling in my face,
Have pluck'd my nipple from his boneless gums,
And dash'd the brains out, had I so sworn as you
Have done to this. (1.7.54–59)

Answer 1

I think we are to understand that he made his oath to Lady Macbeth between the end of Act I Scene V and the start of Act I Scene VI

MACBETH: We will speak further.

LADY MACBETH: Only look up clear; To alter favour ever is to fear: Leave all the rest to me.

Exeunt

I'm fresh from seeing Measure for Measure at the RSC in Stratford on Saturday and was struck by how often there is some phrase which cues up the fact that further discussion is going to take place out of the audience's hearing. 'Let us withdraw together' or 'would by and by have some speech with you' or similar is used as characters leave the stage or centre of focus when the detail of what people might agree doesn't really matter because their actions will be played out for us in due course.

Shakespeare sets things up such that we know people have made plans, without telling us the detail of what those plans are.