The Peshitta's two testaments have different histories. The Old Testament was translated from Hebrew, book by book and evidently by different hands, in a process scholars place mainly in the second and third centuries CE, centred by most reconstructions on Edessa; whether the earliest translators were Jews, Jewish Christians or Christians drawing on Jewish expertise remains debated, since the translation shows knowledge of Jewish exegesis and, in places, affinities with the Targum tradition, while other books hew closely and independently to the Hebrew.
Because it descends from Hebrew rather than Greek, the Peshitta Old Testament stands with the Septuagint and the Vulgate among the primary ancient witnesses to the biblical text, and its readings are cited in every serious apparatus. The New Testament followed another route. The earliest Syriac gospel tradition was dominated by Tatian's Diatessaron, the four gospels woven into one continuous narrative, alongside separated-gospel versions now called the Old Syriac; the Peshitta New Testament, emerging by the early fifth century, replaced both with a revision toward the Greek text then standard, and did its work so thoroughly that Diatessaron manuscripts were actively withdrawn. Its canon had twenty two books, without 2 Peter, 2 and 3 John, Jude and Revelation, which entered later Syriac versions; the shorter canon remains the traditional count in the Church of the East.