Nicene and Post-Nicene Fathers, Ser. II, Vol. III:
Life and Works of Rufinus with Jerome's Apology Against Rufinus.: The attack on Epiphanius as a plagiarist of Origen is an outrage on the Bishops generally. Origen never wrote 6000 books.

22. Who are these men who are wont to dispute at such great length in the churches, and to write books, and whose discourses and writings are taken wholly from Origen; these men who are afraid of their literary thefts becoming known, and shew ingratitude towards their master, and who therefore deter men of simple mind from reading him? You ought to mention them by name, and designate the men themselves. Are the reverend bishops 3127 Anastasius and Theophilus, Venerius and Chromatius, and the whole council of the Catholics both in the East and in the West, who publicly denounce him as a heretic, to be esteemed to be plagiarists of his books? Are we to believe that, when they preach in the churches, they do not preach the mysteries of the Scriptures, but merely repeat what they have stolen from Origen? Is it not enough for you to disparage them all in general, but you must specially aim the spear of your pen against a reverend and eminent Bishop of the church? Who is this who considers p. 514 that he has a necessity laid on him of reviling Origen, as the Gospel which he must preach among all nations and tongues? this man who proclaimed in the audience of a vast multitude of the brethren that he had read six thousand of his books? You yourself were in the very centre of that multitude and company of the brethren, when, as he complains in his letter, 3128 the monstrous doctrines of Origen were enlarged upon by you. Is it to be imputed to him as a crime that he knows the Greek, the Syrian, the Hebrew, the Egyptian, and in part also the Latin language? Then, I suppose, the Apostles and Apostolic men, who spoke with tongues, are to be condemned; and you who know two languages may deride me who know three. But as for the six thousand books which you pretend that he has read, who will believe that you are speaking the truth, or that he was capable of telling such a lie? If indeed Origen had written six thousand books, it is possible that a man of great learning, who had been trained from his infancy in sacred literature might have read books alien from his own convictions, because he had an inquiring spirit and a love of learning. But how could be read what Origen never wrote? Count up the index contained in the third volume of Eusebius, in which is his life of Pamphilus: you will not find, I do not say six thousand, but not a third of that number of books. I have by me the letter of the above named Pontiff, in which he gives his answer to this calumny of yours uttered when you were still in the East; and it confutes this most manifest falsehood with the open countenance of truth.

Footnotes

Bishops respectively of Rome, Alexandria, Milan, and Aquileia.

Epiphanius to John of Jerusalem. Jerome’s Letters, LI, 3. See also Jerome Against John of Jerusalem, 11, 14.