Sources:

Seneca's "Letters from a Stoic"

Epistulae Morales ad Lucilium better known as Letters from a Stoic, is a collection of letters by Seneca the Younger. Seneca is one of the top Stoic writers, but this book contains ~30 quotations of Epicurus.

Seneca is a sly one… his book of letters is rife with obvious disdain for Epicureans… but on the other hand, it is barely a chapter that goes by that he doesn’t say something along the lines of “Obviously the epicureans are terrible, but I do want to mention this great quote from Epicurus…”

Here is an example:

“I read today, in his works, the following sentence: “If you would enjoy real freedom, you must be the slave of Philosophy.” The man who submits and surrenders himself to her is not kept waiting; he is emancipated on the spot. For the very service of Philosophy is freedom.” — Seneca Letters — Book I

You see read more examples of this on Newepicurean.com.

You can read more about this work on Wikipedia.