Nicene and Post-Nicene Fathers, Ser. II, Vol. III:
Life and Works of Rufinus with Jerome's Apology Against Rufinus.: Pythagoras was rightly quoted by me. I produce some of his sayings.

40. Pythagoras taught, accordingly, that he had himself been originally Euphorbus, and then Callides, thirdly Hermotimus, fourthly Pyrrhus, and lastly Pythagoras; and that those things which had existed, after certain revolutions of time, came into being again; so that nothing in the world should be thought of as new. He said that true philosophy was a meditation on death; that its daily struggle was to draw forth the soul from the prison of the body into liberty: that our learning was recollection, and many other things which Plato works out in his dialogues, especially in the Phædo and Timæus. For Plato, after having formed the Academy and gained innumerable disciples, felt that his philosophy was deficient on many points, and therefore went to Magna Græcia, and there learned the doctrines of Pythagoras from Archytas of Tarentum and Timæus of Locris: and this system he embodied in the elegant form and style which he had learned from Socrates. The whole of this, as we can prove, Origen carried over into his book Περὶ ᾽Αρχῶν, only changing the name. What mistake, then, was I making, when I said that in my youth I had imputed to the Apostles ideas which I had found in Pythagoras, Plato and Empedocles? I did not speak, as you calumniously pretend, of what I had read in the books of Pythagoras, Plato and Empedocles, but of what I p. 539 had read as having existed in their writings, that is, what other men’s writings shewed me to have existed in them. This mode of speaking is quite common. I might say, for instance “The opinions which I read in Socrates I believed to be true,” meaning what I read as his opinions in Plato and others of the Socratic school, though Socrates himself wrote no books. So I might say, I wished to imitate the deeds which I had read of in Alexander and Scipio, 3206 not meaning that they described their own deeds, but that I had read in other men’s works of the deeds which I admired as done by them. Therefore, though I may not be able to inform you of any records of Pythagoras himself as being extant, and proved by the attestation of his son or daughter or others of his disciples, yet you cannot hold me guilty of falsehood, because I said not that I had read his books, but his doctrines. You are quite mistaken if you thought to make this a screen for your falsehood, and to maintain that because I cannot produce any book written by Pythagoras, you have a right to assert that six thousand books of Origen have been lost.

Footnotes

Gesta quæ in Alexandro et Scipione legeram. The Latin construction will bear Jerome’s meaning, but cannot be exactly or elegantly rendered in English.