Here is a proverb that at first glance deals with being truthful or a liar. But as we look at what God is truly saying in this proverb, we see that this goes farther into what we are sharing with others - and whether we are sharing a saving message or a treacherous one that will cost people everything when that day comes upon all the living and the dead.
I am going to comment on this proverb from the last phrase first. The one who utters lies is treacherous. There are those who share things that are not truth on a mere earthly level. This is called lying - and the Bible says that we are not to bear false witness to our neighbor. This simply means we are not to lie to others. So on a mere earthly level it is sinful to speak lies to others. It hurts relationships and betrays trust, which is so important to the very bedrock upon which they are built. But there is a greater sin - and that is being one who speaks lies about things that are beyond the earthly. They lie about heaven - about eternity - about God.
There are those who do this very blatently. Atheists like Richard Dawkins and his fellow mockers write quite voluminously about their opposition to God, His Word, and His salvation. They offer no honest alternative except a life lived for self as God. Thus they bring a very "treacherous" message. They mocking turns people from the things of God - as their flesh desires - and they put God and His gospel out of their minds. They see this as freeing because they no longer think themselves under His law - no longer bridled by His moral restraints. But truly their message is treacherous - because they still must stand at the judgment seat of the One whom they deny. Like the fool who stands in the street denying the existance of the bus barreling down the road toward them - they will find that denying God's existance does nothing to stop the inevitability of His sure and exactlng judgment. On that day how they will be ashamed at their false and damning beliefs - but that day will be too late. The treachery complete - they will join Dawkins and all his mates in hell where they will be tormented for their foolishness and unbelief.
This is not how it has to be though. God speaks a blessing on those who are truthful witnesses. We are told that a truthful witness saves lives. Here is where we see this proverb transcend the physical. True, speaking the truth to someone can save their life physically - as the one who confronts the drug user or alcoholic that there is a horrible demise awaiting them at the end of the road of their lifestyle. But what we are dealing with is a salvation dealing with more than just our physical lives. The truthful witness shares the glorious gospel of Jesus Christ with those who need to hear it. They speak the truth regardless of whether it makes them popular or not. They consider popularity with God infinitely superior to the familiarity of those on earth whose opinion of each other changes as often as the wind changes directions. They know that there is a God and that we must stand before Him on that fateful, yet glorious day. They know that there is nothing that will stand on that day but perfection - the absolute righteousness that God demands when He says, "Therefore be perfect, as God is perfect." (Matthew 5:48) There is no way we can achieve this standing for our righteousness is as filthy rags before the perfect God of this universe. Thus we must turn to His provision - which is the only way and the only hope for us for eternity. He made Him who knew no sin, to become sin on our behalf, so that in Him we might become the righteousness of God. (2 Corinthians 5:20) This is the answer - and it is the only answer acceptable in that day.
The world may hate this, but it is true nevertheless. We have a choice therefore as His children and His ambassadors. Are we going to be treacherous to our friends, neighbors, and associates - or truthful? Do not take this choice lightly - for the difference between obedience and rebellion on this point will often be the difference between others seeing you as a true friend or a treacherous one. It is the difference beteween life and death. Speak the truth saints - whether it is popular or not - whether it is socially acceptable or the word by which you are made a social outcast. There is nothing more important than being a truthful witness who saves lives!