Epiphanius was born 310-20 CE in Israel and later in his early adult years founded a Monastery in Eleutherapolis (in Judea) and remained in this position until he was appointed a Bishop of Constantia of Cyprus in 366 CE. In the last half of the 370s Epiphanius wrote and released his "Panarion" which was a heresiology (see the introduction in Williams, xiii-xxvii). In Book I, section 30, Epiphanius discusses the Jewish Ebionite sect. In the midst of this discussion, Epiphanius diverges into a discussion centered on the Christian works these Ebionites used.
"[3.7] They too accept the Gospel according to Matthew. Like the Corinthians and Merinthians, they too use it alone. They call it, “According to the Hebrews,” and it is true to say that only Matthew expounded and preached the Gospel in the Hebrew language and alphabet in the New Testament. [3.8] But some may already have replied that the Gospel of John too, translated from Greek to Hebrew, is in the Jewish treasuries (γαζοφυλακιοις), I mean the treasuries at Tiberias, and is stored there secretly, as certain Jewish converts have described to me in detail. (9) And not only that, but it is said that the book of the Acts of the Apostles, also translated from Greek to Hebrew, is there in the treasuries (γαζοφυλακιοις), so that the Jews who have read it, the ones who told me about it, have been converted to Christ from this. [4.1] One of them was Josephus—not the ancient Josephus, the author and chronicler, but Josephus of Tiberias,
during the old age of the Emperor Constantine of blessed memory." (Panarion, 30.3.7-4.1; Williams, 133-134)
"Now there was a “gazophylacium”(γαζοφυλακιου) there which was sealed—“gaza” means “treasure” in Hebrew. (8) As many had different notions about this treasury because of its seal, Josephus plucked up the courage to open it unobserved—and found no money, but books money could not buy. (9) Browsing through them he found the Gospel of John translated from Greek to Hebrew, as I said, and the Acts of the Apostles—and Matthew’s Gospel moreover, which is actually Hebrew. After reading from them he was once more distressed in mind, for he was somehow troubled over the faith of Christ. But now he was prodded for two reasons, his reading of the books and the patriarch’s initiation. Still, as often happens, his heart was hardened." (Panarion 30.6.7-9; Williams, 136).
"At this time he lodged next to the church, I don’t know in which city. But he made friends with the bishop there,
unobserved, borrowed the Gospels and read them." (Pan. 30.11.3; Williams, 139)
Those that were hostile to Josephus's flirtations with Christianity and his strict methods of leadership began to look for ways to catch him up. They were finally presented with an opportunity,
very severe as an apostle should be—as I said, this is their name for the rank—and indeed was a reformer, he was always intent on what would make for the establishment of good order and purged and demoted many of the appointed synagogue-heads, priests, elders and “azanites” (meaning their kind of deacons or assistants), many were angry with him. As though in an attempt to pay him back these people took no little trouble to pry into his affairs and find out what he was doing. (5) For this reason a crowd of meddlers burst in upon him at home in his residence, and caught him pouring over the Gospels. They seized the book and grabbed the man, dragged him to the floor with shouts, bore him off to the synagogue with no light mistreatment, and beat him as the Law prescribes. (6) This made his first trial; however, the bishop of the town arrived and got him out." (Pan. 38.11.4-6; Williams, 139)
There are some interesting insights into the interchange between Jewish and Christian communities in the late 3rd and early 4th centuries in Palestine that can be gleaned from this account. The lines between the Jewish and Christian communities were blurred and there appears to have been a considerable amount of interchange. Not only did the Jewish Patriarch have his own secret collection of Christian writings, these were translated from Greek into their own Hebrew dialect. Coupled with this, Josephus had access to the Gospel writings that were part of a local Church's collection even though, at the time he was not a Christian.