This one's about Jesus. But we're guessing you already knew that.
Matthew's Gospel is one of four books about Jesus's life and teachings that wound up in the official Bible. Sure, there are three other books that sound pretty similar, but this one's still unique. Matthew puts his own special spin on Jesus that's a lot different from his friends Mark, Luke, and John. What can we say? Matthew's just a special snowflake.
Christian tradition has always held that Matthew's Gospel was written by none other than Matthew, one of the twelve original disciples (9:9). If that's true, it's a pretty big point in its favor. An eyewitness to the life of Jesus writing about exactly what happened during the Messiah's lifetime? Score!
Wait, not so fast. Most scholars don't think the Gospel was written by the disciple Matthew, let alone by someone who actually knew Jesus. After all, if a member of Jesus's inner circle wrote this book down, why would he have included the same stories as the other gospel writers? You'd think he'd have his own material and that he wouldn't be copying from Mark so much (source, 844).
But that does bring up a good point. Matthew's stories are pretty similar to Mark's and Luke's. In fact, these three are known as the synoptic gospels because they're all kind of the same. (John, on the other hand, is just out there in his own little world. He's just a rebel.)
Why are they all so similar? Well, scholars have a theory for that, too. Coming up with theories is sort of their thing. One possibility is that Mark was the first gospel to be written (probably around 75 CE at the latest). Once Mark had a chance to circulate around Christian circles—and people gave it the big thumbs up—other authors got the idea to write their own versions of the story of Jesus.
Enter Matthew and Luke. These two gospels are probably written around the same time (85 CE) and include lots of the same exact stories as Mark. Matthew has put over 90% of Mark's stories in his gospel for example (source, 198). But, don't worry. It's only plagiarism if God doesn't give you permission. (Don't try that excuse at school, though.)
The trouble is, there are some stories and sayings that don't appear in Mark, but that do show up in both Matthew and Luke (such as "ask, seek, knock" [7:7]). That makes scholars think both Matthew and Luke used another source. They call it Q.
Q stands for "quelle," which is the German word for "source" (and since German biblical scholars came up with it, they got naming rights. Try harder next time, English-speaking scholars). Basically, the thought is that there was once another document that was just a collection of things Jesus said and did. Sadly, if this ever existed, it is lost to us now. Papyrus just isn't meant to stand the test of time.
So what did Matthew do? He took some stories from Mark, some stories from Q added them all together, spiced it up with a bit of his own commentary, and—voilà—a biblical masterpiece was born (source, 816).
So Mark's Gospel wasn't good enough for Matthew, was it? And why not? Well, he does make some changes from the original.
Matthew is writing mainly for a Jewish-Christian audience in transition. These folks embraced Jesus as the messiah, but still wanted to hold onto their Jewish roots. However, many Jews didn't think that the followers of Jesus were properly Jewish anymore. Matthew's community had probably been kicked out of the synagogue and called heretics by their fellow Jews. So, they were pretty down about that.
Because Matthew still sees himself as Jewish, he's very focused on making a case for Jesus as the Jewish messiah (source, 868). He's got Jesus fulfilling biblical prophecies, quoting the Torah, arguing the law with the Pharisees, and living a fully Jewish life. If only there'd been some matzo ball soup at the Last Supper, he'd have been all set.
At the same time that Matthew is looking at his the past and his roots, he's also moving toward the future. His gospel is the only one that goes into detail about the emerging Christian church. He gives rules for being in a Christian community with others. Good stuff like, "If another member of the church sins against you, go and point out the fault when the two of you are alone" (18:15). It's clear that the people needed a little instruction in these areas.
His stories are also chock full of encouragement for the early church (source, 870). Sure, there are tough times ahead. Sure, everyone in the church "will be hated by all because of [Jesus's] name" (10:22). But, fear not. Their reward in heaven in coming. Just hold on for the end of time, guys.
Matthew is branching out a bit past the Jewish community. Other Jews have rejected him and his friends, so now they're beginning to look to Gentiles to spread the good word about Jesus (source, 845) Yes, Jesus came primarily to save Israel, but that didn't totally work out as expected. Now, we're going to Plan B: non-Jews, you're up.
Style-wise, Matthew is on his own. His writing is more polished (at least we think it is—our ancient Greek is sort of rusty). His stories are often shorter and clearer than Mark's, and he also adds in a lot of commentary. In fact, Matthew's typical pattern is to have a whole bunch of stories or parables, followed by a section of theological reflections (source, 869).
Matthew also turns up the volume on the characters quite a bit. The good guys, like Jesus, Peter, and the disciples, get a whole lot more awesome. Jesus is much more dignified and authoritative, and Peter gets added responsibility (though Matthew can't completely ignore important things, like the time he denied knowing Jesus. Whoops). Meanwhile, the bad guys, like the Pharisees, get a whole lot worse. Think of the curse they place on themselves at Jesus's trial. Matthew's not so much for leaving in shades of gray.