Which Gospel was written first, Mark or Matthew? Markan priority is far more widely accepted and has grown in acceptance even among members of the Evangelical Theological Society—see Three Views on the Origins of the Synoptic Gospels.
Case in point. The story of the “raising of many saints” (which is found only in the Gospel of Matthew) makes greater sense if Markan priority is true rather than Matthean priority.
Mark and Matthewʼs stories about Jesusʼ execution right up to the message delivered at the empty tomb are nearly identical. They both depict the same actions and messages of Jesus on the cross, and they both share the same message delivered at the empty tomb. None of the other Gospels share as much as Mark and Matthew do in the above sections. But for all that they share, Matthewʼs tale contains some spectacular bits that Mark lacks. Nor are those spectacular bits found in any other Gospel—they include the earthquake at Jesusʼ death and the raising of many saints who enter the holy city and show themselves to many, guards at Jesusʼ tomb, an earthquake at Jesusʼ tomb, an angel that descends from heaven and sits on top of the rock outside the tomb, and Jewish bribery of the guards. Mark contains none of that, no first earthquake that opens many tombs, no resurrected saints, no guards at Jesusʼ tomb, no second earthquake, no angel descending from heaven and sitting on top of the rock outside the tomb, no Jewish bribery of the guards. (Mark simply says Jesusʼ tomb was empty and a young man was found inside it.) Nor do the other Gospels mention those spectacular bits in Matthew that Mark lacks. In fact all the Gospels lack mention of a single earthquake, let alone two of them. On the other hand, as I already stated, Jesusʼ last words and actions, and the message delivered at the empty tomb (“He has gone before you to Galilee, there you will see him”) are nearly identical in both Mark and Matthew. So it appears Matthew added a lot to a prior Markan story, many of the added bits being of a spectacular nature and corroborated neither by Mark nor by other Gospel writers.
One also canʼt help but notice that following Matthewʼs story of the earthquake that cracks open tombs followed by the raising of many saints, Matthew says:
When the centurion and those with him who were guarding Jesus saw the earthquake and all that had happened, they were terrified, and exclaimed, Surely he was the Son of God! (NIV)
But Mark says:
And when the centurion, who stood there in front of Jesus, heard his cry and saw how he died, he said, Surely this man was the Son of God! (NIV)
So Matthew depicts the centurion along with those with him all “seeing” the “earthquake and all that had happened,” and “they were terrified.” But Mark depicts only the centurion standing “there in front of Jesus,” reacting to “his cry” and seeing “how he died.”
So it looks like Matthew inserted a lot of spectacular bits into his version of the Markan story, even altering what the centurion was looking at when he exclaimed Jesus to be “the Son of God.” Indeed, Matthew seems to have the centurion “and those with him” exclaiming in unison, “Surely he was the Son of God.”
Such additions and edits in Matthew point toward Mark being a more likely primary source.
For further evidence of the priority of Mark one could compare the type and number of miracle tales found in both Mark and Matthew. See this fascinating discussion by a biblioblogger.
