heart
Proverbs 15:2 The tongue of the wise uses knowledge aright: but the mouth of fools pours out foolishness.
Proverbs 16:23 The heart of the wise teaches his mouth, and adds learning to his lips.
1 Kings 3:23-28 Then said the king, The one said, This is my son that lives, and your son is the dead: and the other said, No...
Ecclesiastes 5:2,6 Be not rash with your mouth, and let not your heart be hasty to utter any thing before God: for God is in heaven, and you on earth...
1 Peter 3:15 But sanctify the Lord God in your hearts...
the mouth
Proverbs 10:19 In the multitude of words there wants not sin: but he that refrains his lips is wise.
Proverbs 13:16 Every prudent man deals with knowledge: but a fool lays open his folly.
Proverbs 29:11,20 A fool utters all his mind: but a wise man keeps it in till afterwards...
Ecclesiastes 10:12-14 The words of a wise man's mouth are gracious; but the lips of a fool will swallow up himself...
Matthew 12:34 O generation of vipers, how can you, being evil, speak good things? for out of the abundance of the heart the mouth speaks.
Titus 1:10,11 For there are many unruly and vain talkers and deceivers, specially they of the circumcision...
James 3:6-8 And the tongue is a fire, a world of iniquity: so is the tongue among our members, that it defiles the whole body...
2 Peter 2:18 For when they speak great swelling words of vanity, they allure through the lusts of the flesh, through much wantonness...