Pharisees - On the first notice of them in the New Testament (Matt. 3:7), they are ranked by our Lord with the Sadducees as a "generation of vipers." They were noted for their self-righteousness and their pride (Matt. 9:11; Luke 7:39; 18:11, 12). They were frequently rebuked by our Lord (Matt. 12:39; 16:1-4).
From the very beginning of his ministry the Pharisees showed themselves bitter and persistent enemies of our Lord. They could not bear his doctrines, and they sought by every means to destroy his influence among the people.
And Jesus left them as He doesn't want to argue nor debate with them - this is also the same thing for us we don't need to debate with unbelievers if it's obvious that they are only testing or looking for a hole to put us down.
We serve God because we are saved. Not serve God to be saved. Maintain the doctrines because Jesus is indeed the Mesiah.
In verse 5-12: The disciples were worried because they forgotten the bread, but Jesus reminded them regarding the loaves and feeding of 5 thousand. Now the simple statement of Jesus Christ was "to be on guard against the yeast (false teaching) of the Sadducees and Pharisees". It will lead us astray. Even 1% wrong with (+) 99% right doctrines = everything are still wrong.
Verse 16-20: When Jesus said to Peter "I will give to you the keys of the kingdom of heaven. . ." we should not interpret the Bible as literaly but rather the deeper meaning (listen to the voice of the Holy Spirit) example it doesn't mean that Peter hold the keys of the gates of heaven as what other religion believed (when you're about to enter the heaven you will see San Pedro or Peter). On this verses means that if we believed just like Peter confesses to Jesus "you are the Christ, the Son of the living God" then we will enter the Kingdom of Heaven (as Jesus will give us the keys meaning He will open the door) freely we can open it as the keys are given to us by Jesus Christ means He gave us the authority to open it - if we accept (confesses) and not deny Jesus.
The LORD’s Covenant With Abram
1 After this, the word of the LORD came to Abram in a vision:
“Do not be afraid, Abram.
I am your shield,
your very great reward.”
Why did God say this to Abram (Abraham)? It's because Abram was terrified and for sure he asked "who will be there for me? Who will be my defense against my adversary?" Therefore, God comforted and reminded him of His faithfulness.
We too must not be sacred of whatever we are experiencing and facing right now. Because it's all part of our growing process (spiritually). Let's be positive to know that in our problems and dilemma it is an opportunity to rise into the next level. So be assured that GOD is with you, HE is for you and will be faithful until the end.