Westcott: "Moreover it is known that books were soon translated from Syriac into Greek, and while such an intercourse existed it is scarcely possible to believe that the Scriptures themselves remained untranslated. The same conclusion follows from the controversial writings of Bardesanes¹ which necessarily imply the existence of a Syriac Version of the Bible. Tertullian's example may show that he could hardly have refuted Marcion without the constant use of Scripture. And more than this, Eusebius tells us that Hegisippius 'made quotations from the Gospel according the Hebrews and the Syriac and especially from [writings in] the Hebrew language, showing thereby that he was a Christian of Hebrew descent.' This testimony is valuable coming from the only early Greek writer likely to have been familiar with Syriac literature...

"Ephraem Syrus,² a deacon of Edessa, treats the Version in such a manner as to prove that it was already old in the fourth century. He quotes it as a book of established authority, calling it 'Our Version'; he speaks of the Translator one whose words were familiar; and though the dialects of the East are proverbially permanent, his explanations show that its language even in his time had become partially obsolete.

"Another circumstance serves to exhibit the venerable age of this Version. It was universally received by the different sects into which the Syrian church was divided in the fourth century, and so has continued current even to the present time. All the Syrian Christians, whether belonging to the Nestorian³ , Jacobite⁴ or Roman communion⁵, conspire to hold the Peshitto authoritative and to use it in their public services. It must consequently have been established by familiar use before the first heresies arose or it could not have remained without a rival. Numerous versions or revisions of the New Testament were indeed made afterwards, for Syriac literature is peculiarly rich in this branch of theological criticism; but no one ever supplanted the Peshitto for ecclesiastical purposes...

"But meanwhile there is no sufficient reason to desert the opinion that has obtained the sanction of the most competent scholars, that its formation should be fixed to the first half of the second century. The text, even in its present revised form, exhibits remarkable agreement with the most ancient Greek Manuscripts and the earliest quotations from. The very obscurity that hangs over its origin is a proof of its venerable age, because it shows it grew up spontaneously in Christian congregations, and it was not the result of any public labour. Had it been a work of late date, of the third or fourth century, it is scarcely possible that its history should be so uncertain as it is."

Brooke Foss Westcott, "A General Survey of the History and Canon of the New Testament" (Seventh Edition, 1896), p. 244-8.