"Do not place your hand with an evildoer": This was the practice of the "clean-minded men of Jerusalem." They would not go to a feast until they knew who was going with them, and they would not sign a writ of divorce until they knew who was signing with them. R. Nathan says: "Do not place your hand, etc.": Do not make violence a witness—to exclude evildoers and robbers from being witnesses. As it is written (Devarim 19:16) "If a man of violence rise up against another to testify, etc. … (19) then you shall do to him as he schemed to do, etc."