Matthew 12:34 AMPC
[34] You offspring of vipers! How can you speak good things when you are evil (wicked)? For out of the fullness (the overflow, the superabundance) of the heart the mouth speaks.
Proverbs 4:23-26 AMPC
[23] Keep and guard your heart with all vigilance and above all that you guard, for out of it flow the springs of life. [24] Put away from you false and dishonest speech, and willful and contrary talk put far from you. [25] Let your eyes look right on [with fixed purpose], and let your gaze be straight before you. [26] Consider well the path of your feet, and let all your ways be established and ordered aright.
Colossians 3:15-17 AMPC
[15] And let the peace (soul harmony which comes) from Christ rule (act as umpire continually) in your hearts [deciding and settling with finality all questions that arise in your minds, in that peaceful state] to which as [members of Christ's] one body you were also called [to live]. And be thankful (appreciative), [giving praise to God always]. [16] Let the word [spoken by] Christ (the Messiah) have its home [in your hearts and minds] and dwell in you in [all its] richness, as you teach and admonish and train one another in all insight and intelligence and wisdom [in spiritual things, and as you sing] psalms and hymns and spiritual songs, making melody to God with [His] grace in your hearts. [17] And whatever you do [no matter what it is] in word or deed, do everything in the name of the Lord Jesus and in [dependence upon] His Person, giving praise to God the Father through Him.