"(As you are) going, therefore, disciple all the ethnic groups, baptizing them into the name of the father, and of the son, and of the holy spirit, teaching them to obey all that I have commanded you."
So, he's talking to the eleven disciples here. So the operative question should be, what were the things that he had commanded the disciples?
The first thing Matthew records Jesus saying is to John the Baptist, convincing John to baptize him. If if we construe John to be one of Jesus's disciples, it doesn't seem that this would be one of the commands we're to teach would-be disciples to obey. Jesus has already been baptized, and we don't have to do it again.
The next conversation in Matthew is with Satan in the desert. So these commands again are not the ones we're to teach people to obey. Then he begins his public ministry, proclaiming (to anyone who would listen?) "Repent for the kingdom of heaven has come near." I'd still like to claim that we're not yet talking about the commands in question, for this is more of a general call.
Then, he calls some disciples. This sounds promising. "Follow me," he says to Peter and Andrew. This was a fairly literal command, because these guys (and then James and John after them) stopped what they were doing and started following him around. I guess our challenge now is to translate this to our age: what does it mean to follow Jesus, and how do we teach people to obey it? I'd suggest that Jesus gives us some help here, because the next time Jesus's speech was recorded it is the Sermon on the Mount. And I guess I always had this idea that this was a sermon to a whole bunch of people. But the text is a bit ambiguous on this. For there were crowds around him, it says, and when he saw them he went up the mountain and sat down. Then his DISCIPLES came to him and he taught THEM.
If we take the unity of the book of Matthew seriously, I'd suggest that we ought to take very seriously the commands found here as the prime candidates for what Jesus wanted his disciples to be teaching his future disciples to obey. We'll explore what this might mean in the future.