About 4,500 years ago the world was filled with wickedness. The "Lord saw that the wickedness of man was great on the earth, and that every intent of the thoughts of his heart was only evil continually." God, through Noah a preacher of righteousness, warned the world of the coming judgment. The entire world will be destroyed and everyone will perish, EXCEPT those who go through the door of the ark. People needed to trust what God was telling them, turn away from their unbelief, and obey God by going through the door and getting on the ark.
It's Easy. Believe God. Go Through The Door and Be Saved
The only ones who listened and obeyed were Noah's family. There was plenty of room on the ark. It is huge. It required little physical effort. Just walk up the ramp. But, no one else went through the door... and they died.
Today we have the same choice. The door into the ark foreshadows Jesus Christ. He is the door. God has warned us. Judgment is coming. The only way to be saved is to go through Jesus Christ. Trust Jesus (God). Turn away from the ways if the world, and obey God. Trust that Jesus will save you from God's judgment. He is the only way.
"It is appointed for men to die once and after this comes judgment." - Hebrews 9:27
We all will die. You know judgment is coming.
"...those who do not know God and to those who do not obey the gospel of our Lord Jesus. These will pay the penalty of eternal destruction, away from the presence of the Lord." - 2 Thessalonians 1:8b-9a
To understand what it means to be "away from the presence of the Lord," you need to understand that everything good comes from God. Without God you have nothing good. Even those who totally reject God today, are not away from the Lord. He is being patient, and gives good things to all of His image bearers (you) alive today. But when you die that ends. With Jesus Christ... if you have no gone through the door that is Jesus Christ, you will be away from the presence of the Lord. That means you'll have nothing that is good. Nothing. A cool drink of water, relief from pain, and friends are all good. You won't have them. Even light and having someone, anyone to talk to is good. You won't have them. That's why it's called hell. There is nothing good. You chose to reject Jesus (God). Now, for eternity never ending, you will be completely separated from Him.
"He who does not believe has been judged already, because he has not believed in the name of the only begotten Son of God." - John 3:18
The above quote of John 3:18 does not include the first part of the verse: "He who believes in Him is not judged; he who does not believe has been judged already, because he has not believed in the name of the [f]only begotten Son of God." If you believe in Jesus, you are saved from God's judgment. This does not just mean believe He is real. The demons believe that and tremble (James 2:19). So what do you need to believe?
But these" [the Gospel of John] "have been written so that you may believe that Jesus is the Christ, the Son of God; and that believing you may have life in His name." - John 20:31