The chapter
Simply A sign is demanded and refused. A warning about yeast is misheard as being about bread. Then, at Caesarea Philippi, Peter says who he thinks Jesus is, and immediately afterwards is called Satan.
Context The two halves are joined by one hinge at verse 21: from that time he began to show them that he must suffer. Everything before it is about recognising him, and everything after is about what recognising him costs.
Verses 1-12
Simply Pharisees and Sadducees ask for a sign from heaven and are told they can read the sky but not the times. Crossing over, the disciples find they have no bread and think his warning about yeast is a complaint about it.
Context He answers the misunderstanding by asking them to count: five loaves for five thousand and how many baskets, seven for four thousand and how many. The Gospel is asking its reader to keep the two meals apart, which is why the earlier chapters gave both sets of numbers exactly.
Verses 13-20
Simply He asks who people say he is, then who they say he is. Peter answers that he is the Christ, the Son of the living God, and is told he is Peter, that on this rock the assembly will be built, and that he will be given the keys.
Context These two verses have divided churches for centuries, and this file does not take a side, for a reason that can be checked rather than asserted. The four confessional documents in this app were searched: Trent's two ingested sessions, on justification and on the Eucharist, say nothing about Peter or the keys; the Thirty-Nine Articles and Philaret do not address the question either; and Westminster does speak, at 25.6, in the sharpest possible terms about the Bishop of Rome. A tradition layer built on that would give one voice out of four, and the one voice is a condemnation. So the layer is refused here, exactly as it was on Mark 14 until the missing document arrived.
Verses 21-28
Simply He begins to tell them he must go to Jerusalem, suffer, be killed and be raised. Peter takes him aside to say it will never happen, and is answered with get behind me, Satan. Then: whoever wants to save his life will lose it.
Context The same man is called blessed and then Satan within three verses, and Matthew puts no distance between the two. The reason given is not disloyalty but a way of thinking: he is not minding the things of God but the things of men.