What paradoxical statement made by the witches in the first scene does Macbeth reiterate in the third scene when he first meets the witches?

At the beginning of the play, the witches say, "Fair is
foul, and foul is fair."  Later in Scene 3, Macbeth refers to this line when he says,
"So foul and fair a day I have not seen."  The line is a paradox that means that things
are not always what they seem.  Macbeth appears to be a loyal soldier to Scotland;
however, in the next act, he murders the king whom he claims to love so that he can get
power for himself.  The line is a statement of one of the themes of the play, and
Macbeth brings this up again when he and Banquo meet the witches.  This reiterates the
fact that Macbeth will read into the witches' prophecy in the way that he wants even
though their words may mean something different.