quotation: “how sharper than a serpent’s tooth …”

• https://en.wikiquote.org/wiki/Gratitude

How sharper than a serpent’s tooth it is
To have a thankless child.

William Shakespeare, King Lear (1608), Act I, scene 4, line 310 – https://en.wikiquote.org/wiki/Gratitude

How sharper than a serpent’s tooth
To hear your child make such a fuss.
It isn’t fair —it’s not the truth—
He’s fucked up, yes, but not by us.

Judith Rich Harris, The Nurture Assumption, chapter 15, p. 330 – written in response to Philip Larkin’s poem “This Be The Verse“

I came across this quotation in this novel:

• https://en.wikipedia.org/wiki/Guido_Brunetti_novels#Novels #30
• ISBN 978-1785152627 – https://www.amazon.de/dp/1785152629 – in English
• https://de.wikipedia.org/wiki/Donna_Leon#Die_Brunetti-Romane_2 #30
• ISBN 978-3257071207 – https://www.amazon.de/dp/3257071205 – in German