Psalm 12:6

"And the Words of the Lord are flawless, like silver refined in a furnace of clay, purified seven times."  - Psalm 12:6

Sincerity and truth are extremely valuable because they are so rare. Many people are deceivers, liars, flatterers; they think they will get what they want by deception. 

As a king, David certainly faced his share of such people, who hoped to win his favor and gain advancement through flattery. 

When we feel as though sincerity and truth have nearly gone out of existence , we have one hope-- the Word of God. 

God's Word are as flawless as refined silver. So listen carefully when He speaks.