Tiglath Pileser, the emperor of Assyria, invaded Israel, and Menahem gave him thirty-eight tons of silver to gain his support in strengthening Menahem's power over the country.
If you did this, you would defile the land where you are living. Murder defiles the land, and except by the death of the murderer there is no way to perform the ritual of purification for the land where someone has been murdered.