For more insight into the promise God made to Abraham in which God swore by Himself read Genesis 15 again. In this passage in Genesis, the lamp represents Jesus as the light of the world and the furnace represents the lake of fire.

Ever wondered who Melchizedek is?

Heb 7:1
This Melchizedek was king of Salem and priest of God Most High. He met Abraham returning from the defeat of the kings and blessed him,Ps 110:4
The LORD has sworn and will not change his mind: "You are a priest forever, in the order of Melchizedek."Heb 6:20
where Jesus, who went before us, has entered on our behalf. He has become a high priest forever, in the order of Melchizedek.Heb 7:3
Without father or mother, without genealogy, without beginning of days or end of life, like the Son of God he remains a priest forever.Still wondering??? If so read Hebrews 7 again.

In writing about the priests…
Heb 8:5
They serve at a sanctuary that is a copy and shadow of what is in heaven. This is why Moses was warned when he was about to build the tabernacle: "See to it that you make everything according to the pattern shown you on the mountain."
We could think of the tabernacle as a foreshadowing of what is to come. Or we could think of the tabernacle as a shadow like the shadow of a person. A shadow is not the real thing. It is not a living, breathing, moving thing on its own.

The book of Hebrews is full of references comparing the old covenant to the new. The old law was based on works. A person had to DO something, again and again. The new law is based on grace. Jesus is the one who had to DO something once for all. All we have to DO is believe in Jesus as Lord and Savior.

Heb 9:13-14
The blood of goats and bulls and the ashes of a heifer sprinkled on those who are ceremonially unclean sanctify them so that they are outwardly clean. How much more, then, will the blood of Christ, who through the eternal Spirit offered himself unblemished to God, cleanse our consciences from acts that lead to death, so that we may serve the living God!
Jesus cleanses our conscience. Sacrifices covered up the sin, and only temporarily, they didn’t cleanse the conscience.

Why did the Ark of the Covenant contain the jar of manna, Aaron's staff, and the stone tablets? Obviously they are there as reminders, but reminders of what?

Heb 9:22
In fact, the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness.Heb 9:28
so Christ was sacrificed once to take away the sins of many people; and he will appear a second time,  not to bear sin, but to bring salvation to those who are waiting for him.Jesus has appeared "once for all at the end of the ages..." 
Jesus instituted a new covenant at the end of "ages". These ages represent changes in man's relationship to God. The time periods can be broken down as:
1. Adam and Eve before the fall
2. Adam and Eve after the fall till Noah
3. Noah to Moses
4. Moses to Jesus

"...man is destined to die once, and after that to face judgment..."
The dead know nothing until the judgment. We await the judgment having no knowledge of the passage of time. (see also John 5)
Ecc 9:5
For the living know that they shall die; but the dead do not know anything, nor do they have any more a reward; for their memory is forgotten.

Daily the priests stood to perform their duties implying that they had to continually sacrifice for the people. Jesus on the other hand, sacrificed once for all, mission accomplished, and then He sat at the right hand of God.

Heb 10:14
because by one sacrifice he has made perfect forever those who are being made holy.We are being "made holy".
 We are all “in process”. God isn’t finished with us yet.