Seeking a Sign
The chapter opens with the Pharisees and Sadducees seeking another sign from heaven to let them know if Jesus was the Messiah they were expecting from Old Testament prophecy [Matthew 16:1-12]. His answer was to say that they were able to discern the sky to see whether the weather would be good or not - an early variant of "red sky in the morning, sailors take warning... red sky at night, sailors delight" but they were unable to discern all of the prophecies that He was fulfilling. He continues that if their heart was tuned to God, they would know the truth, but that since they were a wicked and adulterous generation they needed something concrete that could in no way be misconstrued before they would give their allegiance.
After describing their generation, Jesus told them again that the only sign that would be given to them was that of the prophet Jonah and then He and the disciples left them. Clearly, Jesus knew what He was talking about when He told them the sign, but I'm pretty sure it would have confused the disciples, which is why at the end of the chapter He starts filling them in on what is going to happen to Him in Jerusalem.
Just as Jonah drowned and was dead, swallowed by a fish, spewed up on the beach, and resurrected, so Jesus would die on the cross, be buried for three days, and would then be resurrected. This is the sign to which Jesus referred.
He fulfilled this sign, as described earlier, but to save you looking back He was buried on Wednesday before sunset. From then to Thursday sunset was the special sabbath of the Passover. Thursday sunset to Friday sunset was a normal day when the women could prepare to anoint His body. Friday sunset to Saturday sunset was the third Jewish day (sunset-sunset) and Jesus was resurrected after sunset Saturday. The women discovered the missing body on their first day of the week, Sunday morning. What a marvelous sign, and the Roman army couldn't keep it from happening even with their posted guards.
So when Jesus and the disciples got to the other side of the sea of Galilee at Magdala, Jesus warned the disciples to watch out for the leaven of the Pharisees and Sadducees. By that, He meant to beware of their false doctrines.
Since they hadn't brought any bread with them, the disciples wrongly assumed they were being chastised for not bring food and they were talking to each other about it. But Jesus knew what they were whispering about and reminded them of the miracles of the five loaves and seven loaves that He had multiplied to feed thousands of people. Then they realized He was speaking of their doctrines.
On Jesus' Identity
As they moved on to Caesarea Philippi, Jesus finally fully reveals His identity to the disciples. He starts by asking them what the opinion of the people are as to who He is [Matthew 16:13-20]. They replied that some said John the Baptist and others named other prophets, reincarnated, I guess. I've never understood people who claimed He might be John the Baptist as they were both seen together, but clearly the ideas about Jesus were just as odd as a few denominations hold today.
Jesus then wanted to know who His disciples said He was. Simon Peter answers and declares Him to be the Christ, the Son of the living God. Literally the anointed one, the Son of God.
Jesus praises Simon Barjona (son of Jonah) for his answer. Peter is referred to as a little rock, but Jesus declares that His church would be founded on Jesus, a cornerstone that the gates of hell would be unable to prevail against. Peter did have a special place in the early church, as Jesus evaluation of Peter was to put him in a position of authority (having the keys) to carry out the establishment of Christ's church.
The binding and loosing simply means that Peter and the disciples were to work together under the Holy Spirit's direction to implement the will of the Father. When they would bind (or declare something to be forbidden), it was only to be done when the Father in heaven had so directed and was also bound or forbidden in heaven. Likewise, when they would loose (or declare something to be permitted), it was only to be done when the Father had determined it was already allowed in heaven.
Clearly, there have been instances in the church history, where those entrusted with the authority of God in the position of the Pope and Bishops (successors in spirit to Peter and the disciples) have failed to act in God's will. The same can be said of various individuals in authority in every denomination. There have been way too many political and moral lapses in the church. And this has caused the church to fracture into many smaller groups, all part of Christ's church, but no longer united together as a single body.
I'm far from perfect myself. I'd hate to be a Pope and have to live out eternity knowing how I had fallen short. And to be clear, I know I've fallen short, just like every other Christian in one way or another. My reach is much smaller than that of a church leader. But just like the church leaders such as the Pope, we'll have to live out our eternities knowing how we have caused people to stumble and perhaps reject Christ to their eternal destruction. No matter how much good you do, that will weigh on you forever.
At this point, I suspect the church will remain divided into various branches until we are all united together in heaven and God lets everybody know exactly what is going to be from that point on. I suspect it will be a shock for everyone, as probably no denomination is 100% in line with God's idea of church in all aspects.
I do wish that we could make an effort to unite now though. It is far easier for Satan to attack in ambushes that wouldn't weaken the church as a whole, but which might weaken a particular body or denomination of believers. Truly, he cannot bring down the church. Even when the anti-Christ is in control, he won't be able to stop people from turning to Christ. But he can certainly do damage. Even if a worldwide reunification seems out of reach, work on your local level to plan events and outreaches together.
Jesus Warns the Disciples About His Future
After Peter's declaration, Jesus begins to let the disciples know what was in His future. He told them He had to go to Jerusalem, and that He would be accused and tortured, killed, and resurrected again on the third day. Peter, who had just been promoted above the other disciples, said that this could never happen. Jesus had to rebuke the spirit in Peter that was in rebellion to what Jesus had said must happen. Jesus told Peter that Peter was more interested in the things of man than of God.
Jesus then tells the disciples that if they were to really choose to follow Him, they would need to take up the cross and follow Him. If they sought to save their life on earth, they would lose it in eternity. If they lost their life on earth for the sake of Jesus, they would save it in eternity. Of the disciples who survived the immediate aftermath of His crucifixion, not including Judas who committed suicide, only John died a natural death. All the rest were killed.
But Jesus also said a very profound thing at this juncture. What does it matter if a man gains the entire world, but ends up in hell? There are many people today who are certainly trying to get as much of the world as they can possibly get. When the fullness of time is come, if they have rejected Christ, they will have an eternity to contemplate their bad choices.
Eventually, Jesus will come in glory and with His faithful angels to reward everyone for what they have done. Angels will also be active in the tribulation period post-rapture, when judgment will be poured out on the earth. And He ended the chapter by saying that some would not die until they saw the Son of man in glory (speaking of the upcoming transfiguration).