People who do not believe the truth about Jesus, hypocrites who take from widow's, make long insincere prayers, those who blaspheme against the Lord, and those who take the Holy Communion unworthily, all  people who do these things take the risk of being damned.
Jesus gives specific instructions that each of us should go into the world and preach the gospel to everyone (every creature). These instructions are to spread believe, be baptized, and preach the gospel.

• And he said unto them, Go ye into all the world, and preach the gospel to every creature. Mark 16:15

Jesus tells us we will be damned if we do not believe and get baptized
If you want to avoid being damned then you must believe and be baptized.

• He that believeth and is baptized shall be saved; but he that believeth not shall be damned. Mark 16:16

Everyone who does not believe in the truth will be damned
Believing in Jesus (the truth), getting saved, and getting baptized is the only way to avoid being damned.

• That they all might be damned who believed not in the truth, but had pleasure in unrighteousness. 2 TH 2:12
• ​He that believeth and is baptized shall be saved; but he that believeth not shall be damned. Mark 16:16

​Bible Verses About Damnation
​There are three  mentions in the New Testament which mention damnation and who will be damned by God. Hypocrites will receive a greater damnation than others. Specifically mentioned are hypocrites that take away from widow's homes or make long insincere prayers. Blasphemy of the Holy Ghost will most definitely put a person in a position that God never forgives and in danger of eternal damnation. The third mention of damnation is taking communion if you are not worthy of  it.  Communion is the ritual where bread and wine are served to represent the body and blood of Christ's sacrifice.
Definition of Damnation
According to Mirriam Webster Dictionary-The word damnation means "the act of damning : the state of being damned" In other words, if you are damned you are condemned by God which means you will suffer punishment for eternity if you are not saved and in some cases you may even suffer damnation for these things if you do them after you are saved. 
Bible verses with the word Damnation
1. Hypocrites receive a greater damnation
Hypocrites that take away the widow's houses, make long insincere prayer's will receive a greater damnation.

• Woe unto you, scribes and Pharisees, hypocrites! for ye devour widow's houses, and for a pretence make long prayer: therefore ye shall receive the greater damnation. Mt. 23:14

2. Blaspheme of the Holy Ghost will guarantee you eternal damnation
If you blaspheme against the Holy Ghost you are in danger of eternal damnation.

• But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation:Mark 3:29

Definition of Blaspheme according to the Mirriam Webster dictionary is to speak of or address with irreverence
3.  Taking communion (wafer-represents the Lord's Jesus's body and wine-represents the Lord Jesus's blood). If you do this ritual unworthily it will bring damnation upon you
Eating and drinking the wine and wafer of communion without being saved, without considering all that our Lord Jesus suffered for our sake will bring damnation upon themselves.

• For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord's body I Cor. 11:29

Related Topics

Bible Verses About Damnation

Curses

Keys to Blessings

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