Eternal sin
In Christian hamartiology, eternal sins, unforgivable sins, or unpardonable sins are sins which will not be forgiven by God. One eternal or unforgivable sin (blasphemy against the Holy Spirit) is specified in several passages of the Synoptic Gospels, including , , and .
Thou shalt not bear false witness against thy neighbour
To keep “a clear conscience toward God and toward men”(Acts 24:16), Christians must follow Christ's example “to bear witness to the truth.”(John 18:37) The Christian is not to “be ashamed then of testifying to our Lord.”(2 Timothy 1:8) In situations that require witness to the faith, the Christian must profess it without equivocation. Christian witness to the Gospel and the obligations that flow from it are an act of justice that establishes the truth or makes it known. Catholic teaching regards martyrdom as the supreme witness given to the truth of the faith: it means bearing witness even unto death.
Christ's disciples have "put on the new man, created after the likeness of God in true righteousness and holiness."(Ephesians 4:24) By "putting away falsehood," they are to "put away all malice and all guile and insincerity and envy and all slander." (Ephesians 4:25, 1 Peter 2:1)
Public statements contrary to the truth take on a particular gravity. In court it becomes false witness. (Proverbs 19:9) False statements under oath are perjury. Acts such as these contribute to condemnation of the innocent, exoneration of the guilty, or the increased punishment of the accused. (Proverbs 18:5) These are great sins, because they gravely compromise the exercise of justice and the fairness of judicial decisions.