What does Psalm 55:17 mean?

Though David faced danger (Psalm 55:2–5) and betrayal (Psalm 55:12–13), he did not lose all hope. Even in these dire circumstances, he trusted the Lord to keep him safe. This faith is not blind or baseless; David knew God would keep His promises about David's continued reign as king (2 Samuel 7:9, 11). This brought him back to trusting prayer, despite his own fear (Psalm 55:16). David knew his words were not falling on deaf ears; he fully relied on God to hear and to respond.

Here, David describes his approach using the expression "evening and morning and at noon." This most likely means "continually" or "all the time." Parallel English expressions say we are doing something "day and night" or "from sunrise to sunset." The New Testament does not specify precise times for Christians to pray, but 1 Thessalonians 5:17 instructs Christians to "pray without ceasing."

However, this might also mean David engaged in prayer according to a deliberate schedule. Devout Jews in the ancient world observed certain hours of prayer, typically morning, afternoon, and evening. Daniel 6:10 indicates that the prophet Daniel "got down on his knees three times a day and prayed and gave thanks before his God." As in the case of David, Daniel's habit of praying served him well in the face of peril. Acts 3:1 points out that Peter and John, Jews who became followers of Jesus, "were going up to the temple at the hour of prayer, the ninth hour." They, too, practiced the habit of praying consistently even under severe circumstances.