Before I start here, I want to remind you of something that is easy to forget. When the Bible was written, it was NOT written in chapter and verse. In other words, the original human hands who penned the words of the Bible (under the inspiration of God), wrote in narrative form, or some poetic form, but did not divide their writings into chapters and verses. Those were added later.
The transition from chapter 4 to chapter 5 is one of those places where you can't just start reading in 5:1. The Writer is saying something that is a conuous thought and to read 5 without the context of 4 is to not gain the full meaning. Chapter 4 ends by telling us that we have a high priest who is able to understand us completely - including our temptations - but who never experienced sin. Therefore, we can approach God with confidence, knowing that He can and will issue grace and mercy with a total appreciation for our circumstances.
Chapter 5 is a continuation of that thought. Every high priest is selected from men (at the time, only men could be priests), and his role was to 'stand in' for ordinary people. The high priest was a mediator between regular sinners and God. There was a chasm: people who fell short of God's glory stood on one side, God who is flawless on the other. And never the twain shall meet. The role of the priest was to be an intercessor on our behalf, offer sacrifices for our sin, and, in the words of the Writer, to 'represent' us before God. Until Jesus, the high priest was one of us - selected among men. But in Jesus, we get a High Priest who stands on BOTH sides, and brings them together. He was called of God and is now our 'priest forever' (v.6). No longer do you require the pastor, a priest, the bishop, deacon, elder or Pope. You only require the representation of Jesus Christ, to whom you have access.
The Writer invokes the memory of Melchizedek. This is a largly legendary and mysterious figure who shows up briefly in Genesis 14. (you should go read it). Abram (who later becomes Abraham) had just rescued his nephew by defeating some armies in battle. Melchizedek, who is the 'Priest of the Most High God' and the King of Salem, meets with Abram, who gives Melchizedek a tenth of everything he has, presumably as an act of worship. Incidentally, this represents the first tithe and is an indication of Abram's devotion to God and God's representative (the Priest). Melchizedek is mentioned once in Psalm 110 and then by the Writer of Hebrews. That's it. Much has been written about him, but its largely speculation. We only know what is written in the few verses of Scripture which name him.
The chapter closes with some hard words about growing up and maturity. The Writer says, "look, I'd like to explain these truths better, but you can't handle it. You ought to be able to track with me, but you are are still acting like babies. In fact, you need to go back to basics and re-learn the elementary truths of God all over again!" It's a harsh teaching, here. But let's consider the practical application. I will pose these as questions for reflection you should ask yourself and ask God to reveal the truth to you about them:
How mature am I when it comes to matters of faith?
How dedicated am I to learning spiritual truth?
How much time do I devote to studying and learning (reading, reading the Bible, studying the Bible with friends - maybe in small group, etc.)?
Do I allow myself to be stretched by new experiences that God wants to give me, or do I stay comfortably in my safety zone?
What is one thing I could do in the next week that would take a small step of growth towards maturing in my faith?
What is one thing I could do in the next month that would represent a step of moderate growth towards maturity?
What is one thing I could do in the next year that would be a huge step of growth?