Nicene and Post-Nicene Fathers, Ser. II, Vol. III:
Life and Works of Rufinus with Jerome's Apology Against Rufinus.: As to the letter of Pope Anastasius condemning you, you will find that it is genuine.

20. In the matter of the letter of the pope Anastasius, you seem to have come on a slippery place; you walk unsteadily, and do not see where to plant your feet. At one moment you say that it must have been written by me; at another that it ought to have been transmitted to you by him to whom it was sent. Then again you charge the writer with injustice; or you protest that it matters nothing to you whether he wrote it or not, since you hold his predecessor’s testimonial, and, while Rome was begging you to give her the honor of your presence, you disdained her through love of your own little town. If you have any suspicion that the letter was forged by me, why do you not ask for it in the chartulary of the Roman See and then, when you discover that it was not written by the bishop, hold me manifestly guilty of the crime? You would then instead of trying to bind me with cobwebs, hold me fast bound in a net of strong cords. But if it is as written by the Bishop of Rome, it is an act of folly on your part to ask for a copy of the letter from one to whom it was not sent, and not from him who sent it, and to send to the East for evidence the source of which you have in your own country. You had better go to Rome and expostulate with him as to the reproach which he has directed against you when you were both absent and innocent. You might first point out that he had refused to accept your exposition of faith, which, as you say, all Italy has approved, and that he made no use of your literary cudgel against the dogs you spoke of. Next, you might complain that he had sent to the East a letter aimed at you which branded you with the mark of heresy, and said that by your translation of Origen’s books Περὶ ᾽Αρχῶν the Roman church which had received the work in its simplicity was in danger of losing the sincerity of faith which it had learned from the Apostle; and that he had raised yet more ill will against you by daring to condemn this very book, though it was fortified by the attestation of your Preface. It is no light thing that the pontiff of so great a city should have fastened this charge upon you or have rashly taken it up when made by another. You should go about the streets vociferating and crying over and over again, “It is not my book, or, if it is, the uncorrected sheets were stolen by Eusebius. I published it differently, indeed I did not publish it at all; I gave it to nobody, or at all events to few; and my enemy was so unscrupulous and my friends so negligent, that all the copies alike were falsified by him.” This, my dearest brother, is what you ought to have done, not to turn your back upon him and to direct the arrows of your abuse across the sea against me; for how can it cure your wounds that I should be wounded? Does it comfort a man who is stricken for death to see his friend dying with him?