Help with this cliche please!!!!

To wash one's hands of something.

Also, perhaps the concept of "thumbs down" - that gesture was used in the coliseum to indicate whether or not the losing gladiator lived or died.

Or perhaps when Peter denied Christ - "three times before the cock crowed." Peter denied knowing Christ and having anything to do with him after Jesus was captured and on trial.

I think lmur has the better answer here -- the clue mentions Pontius Pilate and it was he who "washed his hands" of the problem of Jesus' fate.