If he is a liar, a talebearer, a railer, a flatterer or a jester

(Letters of John Newton)

There is, perhaps, no one test or proof of the reality of a work of grace upon the heart, more simple, clear and infallible—than the general tenor of our speech; for our Lord's aphorism is of certain and universal application, that "out of the abundance of the heart—the mouth speaks."

To the same purpose, the apostle James proposes to all who make a profession of the gospel, a searching criterion of their sincerity, when he says, "If anyone considers himself religious, and yet does not keep a tight bridle on his tongue—he deceives himself and his religion is worthless!" James supposes that the grace of God in a true believer will check the evils of the heart, and prevent them from breaking out by the tongue.

The grace of God will necessarily influence and govern the tongues of those who partake of it, in what they say when they speak of God, of themselves, and of or to their fellow-creatures.

Having seen a glimpse of the holiness and majesty, the glory and the grace, of the great God with whom they have to do—their hearts are impressed with reverence, and therefore there is a seriousness in their language. They cannot speak lightly of God, or of His ways. One would suppose that no person, who even but seems to be pious, can directly and expressly profane His glorious name. But there is a careless and flippant manner of speaking of the great God, which is very disgusting and very suspicious. Likewise, the hearts of believers teach their mouths to speak honorably of God under all their afflictions and crosses, acknowledging the wisdom and the mercy of His painful dispensations. And, if an impatient word escapes them—it grieves and humbles them, as quite unfitting to their situation as His creatures, and especially as sinful creatures, who have always reason to acknowledge, that it is of the Lord's mercy alone—that they are not wholly consumed.

When they speak of themselves, their tongues are bridled, and restrained from boasting. They speak as befits poor, unworthy creatures—because they feel themselves to be such! In what they say, either of their comforts or of their sorrows, sincerity dictates a simplicity which cannot be easily counterfeited.

In what they say of or to others, the tongues of believers are bridled by a heart-felt regard to truth, love and purity.

Where saving grace is in the heart—the tongue will be bridled by the law of TRUTH. It is grievous to see how nearly and readily some professors will venture upon the borders of a lie; either . . .
  to defend their own conduct,
  to avoid some inconvenience,
  to procure a supposed advantage,
  or sometimes merely to embellish a story!
Where instances of this kind are frequent, I hardly know a fouler blot in profession, or which can give a more just warrant to fear that such professors know nothing aright, either of God or themselves! The Lord is a God of truth; and He teaches His servants to hate and abhor lying, and to speak the truth from their hearts. I may add likewise, with regard to promises—that the person, whose simple word may not be safely depended upon—scarcely deserves the name of a Christian!

Where grace is in the heart, the tongue will likewise
be bridled by the law of LOVE. If we love our neighbor—can we lightly speak evil of him, magnify his failings, or use provoking or insulting language to him? Love thinks no evil—but bears, hopes and endures. Love acts by the golden rule, to "Do unto others—what you would like them to do unto you." Those who are under the influence of Christian love, will be gentle and compassionate, disposed to make the most favorable allowances, and of course their tongues will be restrained from the language of malevolence, harsh censure, and slander—which are as familiar to us as our mother tongue—until we are made partakers of the grace of God.

The tongue is also bridled by a regard to PURITY, agreeable to the precepts, "Do not let any unwholesome talk come out of your mouths!" "Nor should there be obscenity, foolish talk or coarse joking!" Ephesians 4:29, 5:4. Grace has taught believers to hate these things! How then can their tongues speak of them?

There are false professors, indeed, who can suit their language to their company. When with the people of God—they call talk very seriously. But at other times, they are well pleased to join in vain, frothy and evil conversation. But this double-mindedness is of itself, sufficient to discredit all their pretenses to a pious character.

Upon the whole, though perfection is not to be expected, though true believers may, on some occasions, speak rashly, and have great cause for humiliation, watchfulness, and prayer, with respect to the government of their tongues; yet Scripture authorizes this conclusion: That, if the tongue is frequently without a bridle; if it may be observed, that a person often speaks . . .
  lightly of God and of divine things,
  proudly of himself, and
  harshly of his fellow-creatures;
if he is a liar, a talebearer, a railer, a flatterer or a jester—then, whatever other good qualities he may seem to possess—his speech betrays him! He deceives himself, and his religion is worthless!

Let us think of these things, and entreat the Lord to cast the salt of His grace into the fountain of our hearts—that the streams of our conversation may be wholesome.