Here is what the people of Israel said after God consumed Korah and his 250 men with fire, and then broke out in plague against the whole congregation which was complaining against Moses and Aaron:
Numbers 17:12-13
And the people of Israel said to Moses, “Behold, we perish, we are undone, we are all undone. Everyone who comes near, who comes near to the tabernacle of the LORD, shall die. Are we all to perish?”
This is like what Isaiah said when he saw the LORD's glory:
Isaiah 6:5
So I said: “Woe is me, for I am undone! Because I am a man of unclean lips, and I dwell in the midst of a people of unclean lips; for my eyes have seen the King, the LORD of hosts.”
The remedy for Isaiah was his sin being taken away because of the coal from the altar touching his unclean lips.
And God's response to the people of Israel is to tell them this:
Numbers 18:1, 7
So the LORD said to Aaron, “You and your sons and your father's house with you shall bear iniquity connected with the sanctuary, and you and your sons with you shall bear iniquity connected with your priesthood. … And you and your sons with you shall guard your priesthood for all that concerns the altar and that is within the veil; and you shall serve. I give your priesthood as a gift, and any outsider who comes near shall be put to death.”
God's answer to Israel was this: you are right; sinners who come near to the holy God, perish. Therefore, only the priests shall draw very near to God, and the Levites shall help them but shall not go into the most holy place.
And so we. On our own, we are undone in the presence of the holy God, who is a consuming fire (Heb.12:29). Yet we have the massive privilege of "drawing near," the very thing that Israel was petrified of because those who drew near, would die. But we in the new covenant get to draw near, because we have a better and greater High Priest. Israel could not draw near through Aaron; they had to stay far away, and have him draw near on their behalf. But by faith in Christ, we are bidden to draw near ourselves to this awesome God:
Hebrews 4:14-16
Since then we have a great high priest who has passed through the heavens, Jesus, the Son of God, let us hold fast our confession. For we do not have a high priest who is unable to sympathize with our weaknesses, but one who in every respect has been tempted as we are, yet without sin. Let us then with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need.
Why can we draw near through Christ? Because his sacrifice of his own body, opened the way through the veil into the Holy of Holies; his blood that was shed gives true forgiveness and makes us truly cleansed:
Hebrews 10:19-22
Therefore, brothers, since we have confidence to enter the holy places by the blood of Jesus, by the new and living way that he opened for us through the curtain, that is, through his flesh, and since we have a great priest over the house of God, let us draw near with a true heart in full assurance of faith, with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.
This truth about God being so holy that sinners are undone and perish in his presence, apart from a mediator-priest with a sacrifice to atone for them -- this is why Jesus is the only way to approach God:
John 14:6
Jesus said to him, “I am the way, and the truth, and the life. No one comes to the Father except through me."
There is no other way to the Father, for he is a consuming fire. Those who attempt to draw near to him apart from Christ, fall into the hands of the living God and perish. God is too holy for anyone to see him, and not die, who has not had his sins atoned for by the only Sacrifice that truly takes away sins.
This is also why we dare not trust in our own righteousness of any sort -- because if even Isaiah the prophet felt undone and about to perish in the presence of God, how much more we! If the only way to come near to God and not die, is through the righteousness and work of Christ, then let me never trust in my own "goodness," nor relate to God as though he saw me in light of my own "doing well" or "doing badly." He sees us as either IN Christ, or APART FROM Christ, nothing else.
Philippians 3:7-10a
But whatever gain I had, I counted as loss for the sake of Christ. Indeed, I count everything as loss because of the surpassing worth of knowing Christ Jesus my Lord. For his sake I have suffered the loss of all things and count them as rubbish, in order that I may gain Christ and be found in him, not having a righteousness of my own that comes from the law, but that which comes through faith in Christ, the righteousness from God that depends on faith— that I may know him …
So come to your Father boldly, boasting in Christ alone! See the gravity of your own sin, not to then focus on yourself, but rather so that you might see the glory of Christ who covers it!