
“He harms himself who does harm to another, and the evil plan is most harmful to the planner.”
οἷ γ᾽ αὐτῷ κακὰ τεύχει ἀνὴρ ἄλλῳ κακὰ τεύχων
ἡ δὲ κακὴ βουλὴ τῷ βουλεύσαντι κακίστη.
The man who does evil to another does evil to himself, and the evil counsel is most evil for him who counsels it.
He for himself weaves woe who weaves for others woe,
and evil counsel recoils on the counsellor. https://archive.org/stream/b24865898#page/432/mode/2up
Source: Works and Days (c. 700 BC), lines 265-266