In this paper, I shall demonstrate some aspects of the borderline between “Jews” and “non-Jews” as exemplified in the interpretations of “goy” (and “‘am,” in some cases) in the biblical quotations by Rabbis and Aphrahat the Persian Sage (fl. first half of 4th century) during Late Antiquity. Taking into account numerous attempts made in the past to draw a line between “Jews” and “non-Jews,” I focus on what Rabbis and Aphrahat regard as “goy” in the biblical quotations. In the Hebrew Bible, “goy” means a) Jews (or, the Israelites), b) unspecified people including Jews, c) non-Jews, or d) unspecified people regardless of whether including Jews or not. After the establishment of Mishna of Rabbi Jehuda, however, the meanings of “goy” have been integrated into the single meaning, gentile or “non-Jews.” In the Hebrew Bible, Aphrahat, translated “goy” into “‘ammah,” the Syriac word corresponding to “‘am” in Hebrew. This means that Aphrahat understands the word “goy” differently from the Rabbis. Analyzing the borderline between “Jews” and “non-Jews” by focusing on Aphrahat, considered to know and use many Jewish traditions, and comparing his borderline with that of the Rabbis in Late Antiquity can help clarify Jewish identity from both the inside and the outside.