Praise be to Allaah.
The fact that you gave her permission does not cancel out
the divorce which you swore would take place or that you made conditional
upon this stipulation that you mention. Going back on your word does not
help you at all, and the divorce remains in effect, if she did what you
wanted to prevent her from doing. If what you intended by divorce was only
to stop her doing it and you did not intend to make her divorce
conditional upon it, then you have to offer expiation for breaking an oath
(kafaarat yameen), because this is the same as an oath.
But if your intention behind what you mentioned was to make
divorce conditional upon her doing this thing, then divorce has taken place,
if she did that on which it was made conditional.
If there were no previous divorces after which this would
bring the total to three, then it is a revocable divorce and the husband has
the right to take her back so long as the ‘iddah has not yet ended. But if
there were previous divorces and this is the third, then it is an
irrevocable divorce and she is not permissible to him until she has been
married to another husband. End quote.
And Allah knows best.