The one who insults me is my sparring partner.

The source

"The one who insults me is my sparring partner." Epictetus said it in Discourses 3.20.9. Translated from the original Greek by Spartan Surfers.

"καὶ ἀπὸ τοῦ λοιδοροῦντος; — τί δʼ ὠφελεῖ τὸν ἀθλητὴν ὁ προσγυμναζόμενος; τὰ μέγιστα. καὶ οὗτος ἐμοῦ προγυμναστὴς γίνεται"

Original Greek, Discourses 3.20.9. Greek: Schenkl 1916 (Teubner) via Perseus.

Who said it

Epictetus (c. 50–135 AD). Born enslaved, became the most influential Stoic teacher of his age. His student Arrian wrote down the Discourses and the Enchiridion.

Questions

Who said "The one who insults me is my sparring partner."?

Epictetus (c. 50–135 AD). Source: Discourses 3.20.9.

What is the original Greek?

καὶ ἀπὸ τοῦ λοιδοροῦντος; — τί δʼ ὠφελεῖ τὸν ἀθλητὴν ὁ προσγυμναζόμενος; τὰ μέγιστα. καὶ οὗτος ἐμοῦ προγυμναστὴς γίνεται. Translated from the original Greek by Spartan Surfers.