What does Psalm 56:10 mean?

These words begin a phrase concluded in the following verse. This echoes the same statement David made earlier in the song (Psalm 56:4). Rather than despair in his hard circumstances (Psalm 56:1–6), David remembered that God knew his struggles (Psalm 56:7–8) and he trusted the Lord to act for good purposes (Psalm 56:9). The "word" David refers to is not simply the written texts of Scripture. David means all of God's doings, dealings, and concerns. The nature and person of the Lord God was the object of David's continual praise.

The second term for God used here is the covenant name, Yahweh, used by God in reference to Himself (Exodus 3:14). During David's life, he was given promises by God (1 Samuel 16:11–13; 2 Samuel 7:8-12). When David faced trouble and danger, he experienced natural fear (Psalm 55:4–6). Yet he also relied on God's promises and chose to trust the Lord rather than despair (Psalm 55:22; 56:8–9).

In his letter to Titus, Paul writes that God cannot lie (Titus 1:2). Of course, not every promise in the entire Bible applies to every believer. Yet those who know Christ as their Savior have enough promises to drive away fear and provide hope and confidence. The apostle Peter writes in 2 Peter 1:3–4: "His divine power has granted to us all things that pertain to life and godliness…by which he has granted to us his precious and very great promises." Hebrews chapter 11 points out many instances of God fulfilling His promises; these are recorded as reasons for living believers to trust the Lord's guarantees.