Origin most modest of writers, hardly ever alludes to himself in his own works; but Eusebius has devoted to him almost the entire sixth book of "Ecclesiastical History". Eusebius was thoroughly acquainted with the life of his hero; he had collected a hundred of his letters; in collaboration with the martyr Pamphilus he had composed the "Apology for Origen"; he dwelt at Caesarea where Origen's library was preserved, and where his memory still lingered; if at times he may be thought somewhat partial, he is undoubtedly well informed. We find some details also in the "Farewell Address" of St. Gregory Thaumaturgus to his master, in the controversies of St. [[Jerome]] and Rufinus, in St. Epiphanius (Haeres., LXIV), and in Photius (Biblioth. Cod. 118). [Source](https://www.newadvent.org/cathen/11306b.htm)