Albert Barnes Commentary Matthew 27:24

"So when Pilate saw that he prevailed nothing, but rather that a tumult was arising, he took water, and washed his hands before the multitude, saying, I am innocent of the blood of this righteous man; see ye [to it]." — Matthew 27:24 (ASV)

He took water, etc. The Jews were accustomed to wash their hands when they wished to show that they were innocent of a crime committed by others (Psalms 26:6). They often used signs to represent their meaning.

Pilate, in doing this, meant to denote that they were guilty of his death, but that he was innocent.

But the mere washing of his hands did not free him from guilt. He was bound as a magistrate to free an innocent man; and whatever the clamour of the Jews might be, he was guilty at the bar of God for allowing the holy Saviour to be led to execution, to gratify the malice of enraged priests and the clamours of a tumultuous populace.

See ye to it. That is, take it upon yourselves. You are responsible for it, if you put him to death.