What Was the Pillar of Cloud and Fire?

QUESTION:  I’m really struggling in reading the Old Testament.  It’s hard, so much that seems weird or wrong!  What I am I supposed to do or learn with all this?  A problem from Numbers 9:15-23, I am trying to understand the Cloud of the Tabernacle.  I do get that this is God working thru a cloud.  However, I don’t understand why the verses speak of how the cloud stays overnight, or can go on for a few days, a month, or a year in verse 22.  Was this for ‘obedience’?  Especially when it said it could linger there for a year.  How in the world can they stay inside for a year?  It doesn’t speak of how long the cloud was there from beginning to end.  Nor does it say the purpose.  Was there something going on in the region that God was protecting the Israelites? 

ANSWER: Thanks for your question.  As you read the Old Testament keep one thing in mind:  you believe in its inspiration and authority ONLY because Jesus did.  Jesus is the lens through which we Christians read and understand the Jewish Scriptures.  Our whole faith is built on what God did after this, in fulfilment of all this.  It’s a set up, and an opening act; it’s not giving us the whole story of who God is, but rather it’s anticipating the full work of Jesus. 
And so the laws especially must be read through the lens of a post-Law covenant which we have in Christ.  This is the record of God’s agreement with one people, the Gospel is a record of God’s agreement with ALL people.  The early apostles were clear that what you’re reading here are “shadows” of the good things we have in Christ.  Read Hebrews 10:1-18 and 1 Cor 10:1-6, to set your mind in a correct posture for your reading of the Old Covenant.  These are not our laws nor our covenant, these are now examples for us, illustrations of the Christian life, inspiration for our journey.  Inspired by the Holy Spirit and useful for correction and training?  Of course!  But only when “used properly” – as Paul says in 1 Tim 1:8.
This won’t take away all the difficulties you read about, but it will help you hold them with a looser hand, as you rest in the knowledge that whatever else God may be, and whatever he was up to with the Israelites, He cannot be different than what I see in Jesus who said, “The Father and I are One”.  Whatever God was up to must have always been pointing at Jesus.  Whatever confusion comes from how God acts in the early stages of biblical revelation, clarity is found in Christ. 
A good article to help you with the Old Testament is:
So about Cloud of the Tabernacle in Numbers, no one knows what that was.  I think you are right that the point of the Cloud moving is simply that the Israelites are learning obedience.  God says go, we go, and it doesn’t matter if we only set camp for a day.  Likewise, God says stay, we stay, even if that’s years at a time in one location.
The other reason for this direct physical manifestation of direction was likely so that they built their trust in Moses as God’s servant.  Moses received so many direct communiques from God that maybe a resentment would build in the people (as it would toward a cult leader, for example).  We know this happened in the Community from time to time (Number 12:1-2).  How can we trust you, Moses, if you’re the ONLY one getting the “messages”??
Now, God disciplined Aaron and Miriam for rebelling against Moses, but that’s only because that they failed to accept the very public confirmations of Moses that God gave, which is exactly what I’m talking about.  To be skeptical of a prophet dictating from God without such confirmation is actually a GOOD reaction, not a bad one!  Historically, with Mohammed in a cave or Joseph Smith with the angel Moroni and golden tablets, few in those movements really challenged the veracity of the messages.  It was just, “trust me, God speaks to me, and you listen.”
Well, unlike those false religions, true religion always has multiple vehicles to attest to the revelation.  True religion is done out in the open.  Biblical faith is built on events, not merely ideas.  With Jesus, we have 4 gospels and the record of hundreds of witnesses to his resurrection.  And when God was calling the people out of slavery he used Moses in a special way – yes – but he did not shy away from proving himself publicly and openly to the WHOLE community.  The point would be to give them confidence that in fact it was God leading them and not just the hair brained scheme of one man, Moses, getting revelations in secret.
So at Sinai we see God proving himself in thunder and provoking awe in Ex 20:18-19, to ALL the people.  So much so, the people want LESS proof, not more!  When was the last time you heard a person say, “I want God to stop talking to me so much in public acts that prove his godhood and power”??  Well, the cloud is another device just like this (a more gentle one perhaps!) that again proves to the community that God is leading them, not Moses.

As to why they moved so much, no one knows.  It seems arbitrary.  Some speculate that the cloud and fire refer to the volcanic activity of the Sinai range.  If you’ve been to Hawaii and observed the active volcanoes there, you know that during the day, all you see of a live volcano from a distance is the smoke, but at night you don’t see the smoke, but rather the fiery glow of molten rock.

Some would therefore say hovering “over the tabernacle” should be read as a euphemism for the connection between the mountain of God and God’s direction to the congregation.  I don’t know if that’s the right way to see it, but it may mean the movement of the pillars were tied in some way to something going on geologically in that region and as you speculate, might therefore have been about their safety.  Other references to the pillars of cloud and fire seem to indicate it could not be connected to the Mountain of God, but was truly mobile, a supernatural phenomena of some kind (Ex 13:21).
The main lesson of the cloud remains a very simple one:  when God says “go” we go.
Finally, I think you might be confused by the KJV reading of verse 22.  When it says they “remained in their tents”, that means more accurately, “They stayed at that campsite and did not move on” as long as the cloud remained over the tabernacle. They did not literally stay “in doors” for months or a year at a time!!
The NLT helpfully renders the verse like this:

Num 9:22-23: Whether the cloud stayed above the Tabernacle for two days, a month, or a year, the people of Israel stayed in camp and did not move on. But as soon as it lifted, they broke camp and moved on.