to show one’s unwillingness to take responsibility for a situation; to give up on or disown something
—When I found out that the leader of the club had stolen all our group’s funds, I tore up my membership card and washed my hands of the whole thing.

Having sentenced Jesus to die, the Jewish leaders took Jesus to Pilate, the Roman governor of Judea. (Judea was the area of Israel in which Jerusalem was located.) They went to Pilate, because the Romans would not allow them to enforce the death penalty on their own. Pilate was reluctant to put Jesus to death, so he tried to set him free. The Jews were celebrating the Passover festival, and it was a custom of the governor during the festival to allow the people to choose a prisoner for him to release. He asked the crowd that had gathered if they wanted Jesus or Barabbas, who was in prison for rioting and committing murder, to go free:

The governor asked them, “Which of the two do you want me to release for you?” And they said, “Barabbas!” Pilate said to them, “Then what should I do with Jesus who is called the Christ?” They all said, “Crucify him!” He asked, “Why? What wrong has he done?” But they shouted more insistently, “Crucify him!”

When Pilate saw that he could do nothing, but that instead a riot was starting, he took some water, washed his hands before the crowd and said, “I am innocent of this man’s blood. You take care of it yourselves!” (Matthew 27:21-24)