We dedicate the merit of this act
And all acts
To the supreme enlightenment
And complete liberation
Of all beings everywhere
Pervading space and time.
So mote it be.
This comes from Sam Webster (See the "Dharma Wrapper" article at OSOGD.org).
It is Tibetan and it is there for a very important reason. Magical work, and particularly invocatory work, has the side effect of getting the Ego off. In order to mitigate this, we offer all of the energy that would otherwise boost our ego to the Cosmos with this Dedication.
In accordance with the "Dharma Wrapper", we insert this toward the end of every ritual in which we can remember to insert it, regardless of whether it has anything to do with the rest of the ritual.
We recite it in unison, with a short pause at the end of every line. The pauses let us catch our breath and make it easier to stay in sync with everybody else in the group.