In the play Macbeth, what does Macbeth mean when he says that God's judgement brings the poisoned chalice to our own lips?

The actual quote is from Macbeth's soliloquy in Act I,
scene vii, in which Macbeth is considering the consequences that will ensue, if he does,
indeed take Duncan's life in order to become King.  You have the gist of it, but here is
the full quote in its context:

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...But in these
cases

We still have judgement here; that we but
teach

Bloody instructions, which being taught,
return

To plague the inventor.  This
even-handed justice

Commends
the ingredients of our poison'd
chalice

To our own
lips.

It is
interesting that you mention "God's judgement," for though Macbeth mentions later in the
speech that Duncan's good deeds in his life will "plead like angels...against/The deep
damnation of his taking off," he does not invoke God when considering how his own
"bloody" actions will come back upon him.

His awareness
that he will not get off scott-free for murder, but rather have that which he does unto
others done back unto him, does seem to have religious connotation, but, again, he is
focused on a natural, "even-handed" sort of justice that awaits every man as a kind of
karmic pay-back for deeds committed.

So, his own actions
will be the "ingredients" mixed together to create the (in Macbeth's case) "poison" that
he himself will drink from his own cup or "chalice."

His
reasoning here is sound, and is born out by the events of the remainder of the play. 
But, even knowing this in advance, Macbeth still decides to kill Duncan.  He
says:

...I
have no spur

To prick the sides of my intent, but
only

Vaulting
ambition...

Ambition is the
operative word here, and it is the cause, for Macbeth, of all the murders yet to come in
the play.  For a more detailed analysis of this speech, please follow the link
below.