1. If you don’t believe in Jesus as the Christ, (Num 14:26-30)
    Jude 1:4-5, Heb 3:17-18

In the Old Testament, the Israelites who left Egypt did not believe in God and complained to God. In the end, they could not enter the land promised by God, Canaan. (Numbers 14:26-30)

Numbers 14:26 And the Lord spake unto Moses and unto Aaron, saying,
27 How long shall I bear with this evil congregation, which murmur against me? I have heard the murmurings of the children of Israel, which they murmur against me.
28 Say unto them, As truly as I live, saith the Lord, as ye have spoken in mine ears, so will I do to you:
29 Your carcases shall fall in this wilderness; and all that were numbered of you, according to your whole number, from twenty years old and upward which have murmured against me.
30 Doubtless ye shall not come into the land, concerning which I sware to make you dwell therein, save Caleb the son of Jephunneh, and Joshua the son of Nun.

Just as in the Old Testament the people of Israel who came out of Egypt were destroyed because they did not believe in God, so those who deny that Jesus is the Christ will also be destroyed. (Jude 1:4-5, Heb 3:17-18)

Jude 1:4 For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ.
5 I will therefore put you in remembrance, though ye once knew this, how that the Lord, having saved the people out of the land of Egypt, afterward destroyed them that believed not.

Heb 3:17 But with whom was he grieved forty years? was it not with them that had sinned, whose carcases fell in the wilderness?
18 And to whom sware he that they should not enter into his rest, but to them that believed not?