“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
Original
οἷ γ᾽ αὐτῷ κακὰ τεύχει ἀνὴρ ἄλλῳ κακὰ τεύχων<br/>ἡ δὲ κακὴ βουλὴ τῷ βουλεύσαντι κακίστη.
Help us to complete the source, original and additional information
Hesiod 61
Greek poetRelated quotes
“My dignity asks him who does me no harm to do me no harm. Of him who harms me it asks nothing.”
Mi dignidad le pide a quien no me hace daño que no me haga daño, y a quien me hace daño no le pide nada.
Voces (1943)

“Love is not always evil, truth to tell;
Though harm he does, he serves the good as well.”
Dunque Amor sempre rio non si ritrova:
Se spesso nuoce, anco talvolta giova.
Canto XXV, stanza 2 (tr. B. Reynolds)
Orlando Furioso (1532)

“Most harm is done by people who are awake.”
The News Quiz, BBC Radio 4, May 16, 2008

31
Sovereign Maxims
Variant: Natural justice is a pledge of reciprocal benefit, to prevent one man from harming or being harmed by another.

“Perhaps it is impossible for a person who does no good not to do harm.”
Source: Uncle Tom's Cabin (1852), Ch. 28.

“There’s not such thing as magic that does no harm.”
Source: The Broken Kingdoms (2011), Chapter 4 “Frustration” (watercolor) (p. 93)

“It's always the good men who do the most harm in the world.”
As quoted in American Heritage (December 1955), p. 44
Context: I disagree with my brother Charles and Theodore Roosevelt. I think that Lee should have been hanged. It was all the worse that he was a good man and a fine character and acted conscientiously. These facts have nothing to do with the case and should not have been allowed to interfere with just penalties. It's always the good men who do the most harm in the world.

“Harm is in us.
Harm in us, but power to arm.
Harm is in us.
Leave it open!”
Song lyrics, The Dreaming (1982)