Two things are quite remarkable about sins of the tongue: one is the severity with which the Bible speaks of them, and the other is the impunity with which Christians indulge in them.
We rightly abhor adultery, theft and murder and such things, but seem to hold that gossip and backbiting are relatively harmless. Yet what does the Scripture say?
Psalm 15:1‑3, A Psalm of David.
“Lord, who may abide in Your tabernacle?
Who may dwell in Your holy hill?
 He who walks uprightly,
And works righteousness,
And speaks the truth in his heart;
 He who does not backbite with his tongue,
Nor does evil to his neighbour,
Nor does he take up a reproach against his friend…”
Backbiting is included in that terrible list of sins committed by those whom God gives up according to Romans 1:28‑32 which includes these words…
“…being filled with all unrighteousness, sexual immorality, wickedness, covetousness, maliciousness; full of envy, murder, strife, deceit, evil‑mindedness; they are whisperers,  backbiters, haters of God, violent, proud, boasters, inventors of evil things, disobedient to parents,..”
Gossip is forbidden in both Old and New Testaments.
“You shall not go about as a talebearer among your people; nor shall you take a stand against the life of your neighbour: I am the Lord.”
“ A talebearer reveals secrets,
But he who is of a faithful spirit conceals a matter.”
Even in civil law speaking in a way to damage another person’s character is a serious offence. In English law libel and slander are both referred to under the general description of ‘defamation’, and a remedy in damages is awarded in civil proceedings. How much more should Christians avoid it? The ethical basis for laws on defamation is found in the ninth commandment forbidding false witness (Ex. 20:16). But slander and gossip are condemned in many places in the Bible.
Here is a selection of relevant scriptures.
“ Whoever secretly slanders his neighbour,
Him I will destroy…”
What a dreadful fate threatened for a ‘respectable sin’!
We are told some of the things God hates in Proverbs 6:16‑19:
“These six things the Lord hates,
Yes, seven are an abomination to Him:
 A proud look, a lying tongue,
Hands that shed innocent blood,
 A heart that devises wicked plans,
Feet that are swift in running to evil,
 A false witness who speaks lies,
And one who sows discord among brethren.”
Have we taken to heart that God hates gossip (v. 19) as much as murder (v. 17)?
We all are aware that an atheist is a fool for “The fool has said in his heart ‘There is no God’”. But had we realized that God says that the slanderer is a fool also?
“ Whoever hides hatred has lying lips,
And whoever spreads slander is a fool.”
No wonder talebearers and slanderers are to be avoided:
“ He who goes about as a talebearer reveals secrets;
Therefore do not associate with one who flatters with his lips.”
Consider what Proverbs 26:20‑23 means:
“ Where there is no wood, the fire goes out;
And where there is no talebearer, strife ceases.”
The implication is that talebearers stir up bad feeling among people.
Do we take the words of Christ in Matthew 12:34‑37 seriously?
“ Brood of vipers! How can you, being evil, speak good things? For out of the abundance of the heart the mouth speaks.  A good man out of the good treasure of his heart brings forth good things, and an evil man out of the evil treasure brings forth evil things.  But I say to you that for every idle word men may speak, they will give account of it in the day of judgment.  For by your words you will be justified, and by your words you will be condemned.”
What a solemn pronouncement!
The New Testament makes clear that the servants of Christ have special responsibilities in this regard. For example, Titus 3:2 instructs the leader…
“…to speak evil of no one, to be peaceable, gentle, showing all humility to all men.”
We may think we are living a respectable ‘religious’ life, but we could be deceiving ourselves as James makes clear.
“ If anyone among you thinks he is religious, and does not bridle his tongue but deceives his own heart, this one’s religion is useless.”
To stay with James for a moment, the following famous passage on the tongue needs to be meditated upon frequently and applied constantly.
“ Even so the tongue is a little member and boasts great things. See how great a forest a little fire kindles!  And the tongue is a fire, a world of iniquity. The tongue is so set among our members that it defiles the whole body, and sets on fire the course of nature; and it is set on fire by hell.  For every kind of beast and bird, of reptile and creature of the sea, is tamed and has been tamed by mankind.  But no man can tame the tongue. It is an unruly evil, full of deadly poison.  With it we bless our God and Father, and with it we curse men, who have been made in the similitude of God.  Out of the same mouth proceed blessing and cursing. My brethren, these things ought not to be so.”
James 4:11 tells us that speaking evil of one another has wider implications:
“Do not speak evil of one another, brethren. He who speaks evil of a brother and judges his brother, speaks evil of the law and judges the law. But if you judge the law, you are not a doer of the law but a judge.”
What else are we told about slander in the Bible? Here are a few points to ponder:
Slander comes from an evil heart (Luke 6:45). The wicked are addicted to it (Psa. 50:16, 19, 20) as are hypocrites (Prov. 11:9). It is a characteristic of the devil (Rev. 12:10), and those who indulge in it are doing the devil’s work for him. Those who indulge in it are fools (Prov. 10:18). Ministers’ wives especially should avoid it (I Tim. 3:11).
The saints should keep their tongues from slander – Psalm 34:13
“ Keep your tongue from evil,
And your lips from speaking deceit.” (Cf. 1 Peter 3:10).
I Timothy 5:19 is a special case of this matter. Ministers are to be protected from malicious gossips.
“ Do not receive an accusation against an elder except from two or three witnesses.”
There are several points to notice here. First, this verse speaks of receiving (not believing) an accusation with a view to investigation and verifying the accusation. It does not mean that the accusation should be believed at first.
Secondly, the word “mouth” indicates a verbal witness, and implies that the accusers must be willing to make the accusation in front of the accused. If they are unwilling to uphold their accusation before the one they accuse then they are gossips and should be disregarded or even rebuked.
William Hendriksen comments on this verse as follows:
19. Now this “honor” which is the elder’s due should express itself also in another way: Never entertain an accusation against an elder unless (it is) supported by two or three witnesses.
An accusation against an elder must be upon -that is, must be based upon the oral testimony of – two or three witnesses. Note that though of old any Israelite was safeguarded against indictment and sentencing unless two or three reliable witnesses testified against him (cf. Deut. 17:6; cf. Num. 35:30…), here (I Tim. 5:19) presbyters are safeguarded even against having to answer a charge (cf. Ex. 23:1 in LXX), unless it be at once supported by two or three witnesses. Lacking such support, the accusation must not even be taken up or entertained. The reputation of the elder must not be unnecessarily damaged, and his work must not suffer unnecessary interruption. (Emphasis added).[i]
Douglas J. W. Milne explains the verse in this way:
Do not entertain an accusation against an elder unless it is brought by two or three witnesses (verse 19). In God’s covenant community of the local church, one member cannot go about slandering another individual, especially if this other member happens to be a leader of the church. The Mosaic legislation to which Paul appeals here guarded against this possibility by
instituting the law of double evidence. By this law a charge against another member of the community would only be considered if two independent witnesses came forward (Deut. 17:6; 19:15). Paul applies the same standard to Christian church life, so as to prevent individuals or groups acting out of prejudice, jealousy or animosity against a church leader who might have acted justly in the discharge of his responsibilities. [ii]
A redoubtable lady (Hannah More) whose life spanned the late eighteenth and early nineteenth centuries, when approached with an item of gossip, serious criticism or slander, would hurry the accuser off to face the accused in order to ascertain the truth of the matter. We may be sure that when her practice became widely known, few would approach her with gossip or false accusations. Oh that we Christians would be more strict in dealing with those who do the devil’s work of slander.
Even in civil law an accusation cannot be upheld without giving the accused an opportunity to defend himself or herself. Yet so often Christians believe what is whispered and “take up a reproach” against another believer without giving that person a chance to deny the accusation.
The Scripture is very clear as to how alleged offences are to be dealt with.
“Moreover if your brother sins against you, go and tell him his fault between you and him alone. If he hears you, you have gained your brother.  But if he will not hear, take with you one or two more, that ‘by the mouth of two or three witnesses every word may be established.’
The offence must never be spread or broadcast beyond those it immediately effects unless it becomes a matter of church discipline. Even then care should be taken not to spread gossip.
In any case, if we have falsely accused a brother or sister, or even believed a false accusation, we should apologize and get right with that person before worshipping God.
Therefore if you bring your gift to the altar, and there remember that your brother has something against you,  leave your gift there before the altar, and go your way. First be reconciled to your brother, and then come and offer your gift.
How easy it is to fall into this sin! We all fail from time to time for, as James says, a person who could control his tongue would be a perfect man. Let us therefore seek to mortify this sin of the flesh.
One final word. A simple test as to whether it is right or not to pass on some titbit (or listen to it) is to pose three questions: First, is it absolutely true? Secondly, is it really necessary? Thirdly, is it truly kind? Will this violate the law of love in 1 Corinthians 13?
There must be very few bits of critical or harmful gossip about another person that easily pass those three tests.