The first Christian writing was "The Sayings of Our Lord," written about 40 AD.
According to the early Christian writers Papias and Eusebius the first gospel was written in Aramaic and was called “The Sayings of Our Lord.” Eusebius gives other information that would date “The Sayings of Our Lord” to about 40 AD. The Didache, recently re-dated by scholars to about 60 AD, quotes sayings of Jesus from a Greek writing called “The Gospel of Our Lord” that must have come from the Aramaic “The Sayings of Our Lord.”
Biblical scholars such as C.C. Torrey, Matthew Black, Frank Zimmermann, and others have written scholarly works on the Aramaic materials that were the basis for much of the New Testament. The Greek gospels of Matthew, Mark, and Luke were written about 65-70 AD and were partly based on “The Sayings of Our Lord,” while the Gospel of John and John’s Revelation were direct translations from earlier Aramaic writings, and the first half of the Acts of the Apostles was based on an Aramaic document.