Psalm 12:6

Ps. 12:6, 
The words of the Lord are pure words,
like silver refined in a furnace on the ground,
purified seven times.

To say that God's words are pure, refined, and purified is to insist that they have no “dross” of lies, flattery, or insincerity: God means what he says; his words are completely pure. This general truth gives bite to his specific promise of v. 7 

Psalm 12:7
You, O Lord, will keep them;
you will guard us from this generation forever.

God Will Guard His Faithful. The psalm closes with assurance: God will protect his faithful followers.

Prov. 30:5
Every word of God proves true;
he is a shield to those who take refuge in him.

Prov. 30:5–6 Every word of God proves true (cf. 2 Sam. 22:31; Ps. 18:30). “Proves true” can also mean “refined” (cf. Ps. 12:6) or “well tried” (Ps. 119:140); the implication is that God's words are a proven foundation for one's life. The proverb's emphasis on every “word” (Hb. ’imrah) underscores the truthfulness, trustworthiness, and reliability of the Bible, not just in its overall message but also of every detail. This verse supplies support for the doctrine of the “plenary” (full, complete) inspiration of Scripture, extending even to “every word.” Thus Prov. 30:6 warns against adding to God's words. The whole of vv. 2–6 thus teaches that human wisdom is limited, that the wisest people recognize their ignorance, that truth resides in the word of God, and that no one should think he is able to enhance the wisdom that God has given.

These Bible verses do not say we have a 100% preserved Greek and Hebrew Text.