'Witnesses' in the Bible

On the evidence of two or three witnesses, he who is to die shall be put to death; he shall not be put to death on the evidence of [only] one witness.

The hand of the witnesses shall be the first against him to put him to death, and afterward the hand of all the people. So you shall remove the evil from among you.

“A single witness shall not appear in a trial against a man for any wrong or any sin which he has committed; [only] on the testimony or evidence of two or three witnesses shall a charge be confirmed.