According to Protestants, what is the lesson being taught by scripture when God killed so many men for looking into the Ark?

I believe there are two options a Christian can live with:

1. there was a reason for those people to die and God knew it, but we don't and won't.
2. They were somehow sinning against God in the issue of "not looking into the sacred things" (Numbers 4:20)

Beyth Shemesh means temple of the sun. They were sun worshipers. When Israel took over, they were supposed to drive out all the inhabitants, but they didn't.

Judges 1:33 Neither did Naphtali drive out the inhabitants of Bethshemesh,

Levites and others of the 12 tribes lived in Bethshemesh, but notice where they put the ark. It was on a large or high stone, implying an altar (verse 14). But not an altar dedicated solely to God. They didn't build an altar to the LORD, they took what was already there and mixed the two.

They "looked" into the ark, not for God, but for their sun-god. The word translated "looked" also means visions and seer.

The KJV translates Strong's H7200 in the following manner: see (879x), look (104x), behold (83x), shew (68x), appear (66x), consider (22x), seer (12x), spy (6x), respect (5x), perceive (5x), provide (4x), regard (4x), enjoy (4x), lo (3x), foreseeth (2x), heed (2x), miscellaneous (74x). https://www.blueletterbible.org/lang/lexicon/lexicon.cfm?Strongs=H7200&t=KJV

In other words, they, from the priest to the laity, were misusing the ark. They thought their status as chosen people to where the cows had brought the ark somehow exempted them from the rules. They thought they could continue to mix sun worship with true worship, mix a high stone with a dedicated to God altar.

After God kills them, they send the ark to Kirth-jearim meaning a city of towns. Even worse in terms of an amalgam of religions. To those men, this ark is just another religion. But Samuel tells them to put away their strange gods and goddesses. They sanctify Eleazar son of Abinadad who are not Levitical priests, but know not to misuse the ark of the covenant as those before had done. There is no mixture here for 20 years.

So, the lesson being taught is do not mingle the profane with the sacred. Don't mix idol worship and true worship. Don't presume God's goodness just because. As Christ taught us, worship in spirit and in truth (John 4:24).

Don’t Lift the Lid on Other People’s Sins

I spent twelve years in prison. During one of the programs I was participating in, there was an exercise involving the development of a detailed histogram of each member’s entire life, detailing all the past sins. Then a public presentation of the histogram with a critique by the entire group. I found this spiritually distasteful and paralleled the story of the men who looked into the Ark.

To understand the lesson being taught by God for looking into the Ark, we must first realize what is in the Ark; second, fathom the meaning of the Ark itself; and third, apprehend why it was so deadly inappropriate for the men of Beth-She-Mesh to look inside.

1) In Hebrews 9:4, the contents of the Ark are listed: the golden pot held manna gathered as food during the Israelites forty years wilderness journey; Aaron’s rod that had budded (Numbers 17); and the tables of the Covenant (the ten commandments – exodus 25:16). All three of these objects are physical reminders of the Israelite’s sins of their past.

Manna: Exodus 16, “The whole congregation…murmured against Moses…I will rain bread from heaven (manna), that I may prove them (prove they are sinners in need of Salvation), whether they will walk in my law or not…for the Lord heareth your murmuring against the Lord…and it came to pass, that there went out some of the people on the Sabbath day to gather (manna), and they found none, and the Lord said unto Moses, how long refuse ye to keep my commandments and my laws…”

Aaron’s Rod: Numbers 17:10, “Bring Aaron’s rod again before the testimony, to be kept for a token against the rebels” (see Numbers 16).

The Tablets of the Covenant (the ten commandments): These are referred to in Scripture as “the law.” The book of Romans tells how “the law” is not only a reminder or our sins, but also manifests our bad deed as sin; “For by the law is the knowledge of sin…for until the law sin was in the world: but sin is not imputed where there is no law…moreover the law entered, that the offense (sin) might abound…I had not known sin, but by the law.”

2) The Ark itself is one of the brightest physical parables God gives in His Word, of His Salvation plan: When God saves a person, He puts past sins into a closed box never to be brought to light again. He has put the “seat of His mercy” on top of the box – on top of our sins. And it is on this seat of mercy in which the high priest, on the Day of Atonement sprinkles the shed blood. The Ark is covered in a layer of gold, representing God’s brilliant righteousness.

3) It is now that it all comes together: our past sins are under the mercy of God, covered by the shed blood, wrapped in God’s cloak of righteousness, never to be seen or remembered again. How presumptuous, how disrespectful of the men of Beth-She-Mesh, to lift the lid of the Covenant and look upon the past sins of their forefathers, to look upon the past sins of someone else, which are their sins also. At the moment the lid opened, their past sins were no longer under the mercy (seat) of God, no longer under the shed blood of the Redeemer, no longer completely wrapped in the golden righteousness of God. In that moment those sins of the past were brought back into the light, forced again into the mind and remembrance of God; and in that moment deserving of God’s swift judgment. And judgement came.

So, with all this understood, why would I want to continue in a program whose main premise is to spend months lifting the lid not only on my past sins but on the past sins of fourteen other inmates. I left that program.

Note: Within six months of my termination from that program, God completely disassembled the whole group: two members died and so many others were terminated for various reasons, that the group was no longer viable and discontinued. The Lord works in mysterious ways.

Sin really did abound when the Law was given in the old testament, and every form of disobedience or sin, as little as it can be, was dealt with strict punishment or Death.

Jesus came to fulfil all laws (Matthew 5:17-20) and destroy sin and death. This means that we no longer live in sin but by Grace and we can walk boldly to his throne (Hebrews 4:16) without fear or guilt like Old Testament people.

The Law has been abolished and Jesus took every judgement upon Himself.