I don't trust al Sadr enough to believe anything he says. He has an ulterior motive.
I don't disagree with that assessment, but it seems to me that this is a no win situation for him.

If violence does stop immediatelly due to this then there is absolutely no doubt in anyone's mind that the MM was behind a majority of the recent violence, not that there was a lot of boubt about that in the first place.

If it continues then it will be percieved that he has lost control of the group.

I think I will be more worried if this does reduce violence.

Even more so if due to the reduced violence, in conjunction with the withdrawal of British forces in the South, the US doesn't apply enough forces there.