In what languages were the books of the Bible first written? And, what language did Jesus speak? The Old Testament (the "Hebrew Bible") was written in Ancient Hebrew and Aramaic. Aramaic is a Semitic language related to Hebrew, but the two are as different from each other as are modern French and Spanish. By the 8th Century B.C. Aramaic was the major language of the Middle East and is spoken today in a particular dialect in a few eastern Mediterranean villages. The Aramaic sections of the Old Testament are within the books Ezra and Daniel and possibly Genesis 31:47 and Jeremiah 10:10-11. Jesus most likely spoke a dialect of Aramaic, and it is probable that he also spoke Hebrew, especially when visiting Judea. The New Testament was written in Koine Greek (the common dialect, a somewhat simplified form of classical Greek). "Nonetheless, NT [New Testament] Greek differs somewhat from Koine Greek owing not only to the influence of Hebrew and Aramaic patterns on the NT authors..., but also to the new connotations of Greek words generated by the process of community formation in early Christianity. Moreover, NT Greek varies from book to book as a result of each author's educational level and familiarity with Koine Greek..." [from "Greek, New Testament, History of the Ancient Greek Language" in the HarperCollins Bible Dictionary, p. 389]
Complex linguistic discoveries and refinements lead to regularly appearing new Bible translations into contemporary languages; a challenging factor in the translation process is that today's ever-changing languages are products of current cultures very different from their ancient, biblical predecessors. With regard to the New Testament especially, as new translations and interpretations are developed, biblical scholars continue to face the task of discerning the Semitic/Aramaic sense that may underlie the Hellenistic/Koine Greek.