The Difference Between a Redeemed and Unredeemed Tongue

In his commentary on Colossians, John MacArthur offers a helpful summary of what the Bible has to say about the tongue of the redeemed and unredeemed. His basic point is simple: you ought to be able to tell the nature of one's heart by their mouth. He writes:

When our Lord told the Pharisees that ‘the mouth speaks out of that which fills the heart’ (Matt. 12:34), He gave an important spiritual principle: Speech will reflect the kind of person one is. Because the tongue can speak so easily and is difficult to control, a person’s speech becomes the truest indicator of his spiritual state (cf. Matt. 12:37).

He then goes on to highlight the characteristics of an unredeemed tongue which is prone to:

• evil (Prov. 15:28)
• sexual immorality (Prov. 5:3)
• deceit (Jer. 9:8)
• curses (Ps. 10:7)
• oppression (Ps. 10:7)
• lies (Prov. 12:22)
• destruction (Prov. 11:11)
• vanity (2 Pet. 2:18)
• flattery (Prov. 26:28)
• foolishness (Prov. 15:2)
• madness (Eccles. 10:12-13)
• carelessness (Matt. 12:36)
• boasting (Ro. 1:30)
• false doctrine (Titus 1:11)
• evil plots (Ps. 37:12)
• hatred (Ps. 109:3)
• too many words (Eccles. 10:14)
• gossip (Prov. 26:22)

He then does the same for the redeemed tongue which is characterized by

•  confession of sin (1 John 1:9)
• confession of Christ (Rom. 10:9-10)
• edifying speech (Eph. 4:29
• talk of God’s law (Ex. 13:9)
• praise to God (Heb. 13:15)
• blessing of enemies (1 Pet. 3:9)
• talk about God (Ps. 66:16)
• wisdom and kindness (Prov. 31:26)
• gentleness (prov. 15:1).

He then concludes: It takes as its model the Lord Jesus, who spoke instructively (Matt. 5:2), graciously (Luke 4:22), blamelessly (Luke 11:54), and without deceit (1 Pet. 2:22). (177-178)