Matthew was written in 37AD and you say that was decades after?
The gospel of Matthew was written decades after Christ.
Date The Gospel Of Matthew Was Written
The tradition handed down from the ancient church is that Matthew’s gospel was the first of the gospels to have been written. The actual date of its writing is unknown. A date of A.D. 50 to 60 has been suggested as a probable date. The gospel itself contains no internal evidence that would make it possible to determine the date when it was written.
An early date of A.D. 50 to 60 is a good probability in light of what is known about the Gospel of John. The manner in which the apostle John wrote his gospel makes him indirectly a credible witness to such a possible early date. John wrote his gospel in Ephesus around A.D. 85. It is apparent that by that time he was quite familiar with the contents of the three synoptic Gospels of Matthew, Mark, and Luke and that he accepted them as Scripture. For he wrote his gospel in a manner which supposed and required his readers’ previous knowledge with those synoptic gospels. John skipped much of the material covered in the three synoptic gospels and filled in the blanks and the gaps that the other three gospels did not cover. Based on this manner in which John wrote his gospel in A.D. 85, the Gospel of Matthew, as well as those of Mark and Luke, must have been written prior to that date.
http://www.christianinconnect.com/matthew.htm