See here, 1. What pains men take to do mischief to others. As they put a force upon themselves by concealing their design with a profession of friendship, so they put themselves to a great deal of labour to bring it about; it is digging a pit, it is rolling a stone, hard work, and yet men will not stick at it to gratify their passion and revenge. 2. What preparation they hereby make of mischief to themselves. Their violent dealing will return upon their own heads; they shall themselves fall into the pit they digged, and the stone they rolled will return upon them, Psalm 7:15-16. The righteous God will take the wise, not only in their own craftiness, but in their own cruelty. It is the plotter's doom. Haman is hanged on a gallows of his own preparing.
—————nec lex est justior ulla Quam necis artifices arte perire sua— Nor is there any law more just than that the contrivers of destruction should perish by their own arts.