I assume that you are referring to the speech Macbeth makes at the end of Act Four, scene one, in Shakespeare's play, Macbeth, when Macbeth decides how he will proceed with the new information he has received, specifically from Lennox regarding Macduff's flight to England.
By going to England, Macduff, a good and decent man who loves his country, is branded a traitor—Macbeth knows that Malcolm is in England enjoying the hospitality and protection of Edward the Confessor.
Macbeth's speech is delivered as an "aside," so that no one else on stage can hear him, but the audience knows what he is thinking. Macbeth first comments (as he personifies time, as "anticipating") that "Time" knows Macbeth's plans already. He admits that putting off one's actions never brings about the results someone wants. He promises that from this time on, if he conceives a plan, he will act on it—carry it out—instantly.
[Aside.] Time, thou anticipatest my dread exploits.
The flighty purpose never is o'ertook
Unless the deed go with it. From this moment
The very firstlings of my heart shall be
The firstlings of my hand. And even now,
To crown my thoughts with acts, be it thought and done… (IV.i.61-65)
Macbeth intends to start joining his thought and actions right now. Macbeth plans to surprise and seize Macduff's castle and its occupants, and then kill anyone in there at that time: Macduff's wife, his children and his servants—anyone that can be connected to Macduff in any way. We see in this that Macbeth has truly gone mad —killing not Macduff, but his family—just to punish Macduff's rejection of Macbeth as his King, as well as the true King of Scotland.
The castle of Macduff I will surprise,
Seize upon Fife; give to the edge o’ the sword
His wife, his babes, and all unfortunate souls
That trace him in his line. (168-170)
Macbeth promises that he will not "boast" foolishly about what he intends to do, but will carry out this deadly deed before he has a chance to think about it or before his temper cools down. He wants no more visions, now; he just wants to strike quickly.
No boasting like a fool;
This deed I'll do before this purpose cool.
But no more sights!–Where are these gentlemen?
Come, bring me where they are. (170-173)
The witches' second set of predictions have given Macbeth a sense of invincibility—but it is a "false sense of security," as Hecate had hoped. Macbeth is just as committed to his purpose as ever before. He believes no one can touch him.