Psalm 119:89:

For ever, O LORD, thy word is settled in heaven.

See also:

Forever Settled
If Jesus Were to Appear to You...
How Can I Get Rid of Unbelief?
Objection: You Never Know What God Will Do
Objection: The Faith Confession Movement Tends Strongly to Emphasize God’s Faithfulness at the Expense of God’s Freedom
Objection: Faith Teaching Reduces a Personal God to a Set of Formulas