The words of the LORD are pure words, like silver tried in a furnace of earth, purified seven times. You shall keep them, O LORD, You shall preserve them from this generation forever.
David began this psalm lamenting the disappearance of godly people and the increase of evil communication. Thankfully, eventually God will intervene.
Here David contrasts the purity of God’s communication and promises. “The assurance of the godly ultimately lies in God’s promises. His ‘words’ are pure (‘flawless’), refined like silver that has been subjected to a sevenfold process of purification (cf. 18:30; 119:140). Over against the lies, deceptions, treachery, perverse speech, and scheming of the wicked is God’s word!” (Zondervan NIV Bible Commentary).
For more about how we grow in purity and holiness, see “What Is Conversion?”