What does Psalm 39:1 mean?

This psalm does not explain exactly why David is struggling. This first verse suggests that he is being confronted with wicked people, possibly critics or enemies. If these events were triggered by David's sin (Psalm 39:8–11) he would have multiple reasons for distress. David's concern about his speech likely comes in two forms. In one way, he would have worried that his words towards these wicked ones would be unfair; they might provide further reason to claim offense. In another, David may have been worried that his anger would cause him to speak wrongly of God, or about God.

Rather than speaking words which would be regretted later, David has committed to being silent. A "muzzle" is attached to an animal's face to keep it from biting. In the spirit of passages such as James 3:1–5, David chooses to restrain his speech rather than risk losing control. It can be exceedingly difficult to choose silence, but this is often the best option when dealing with irrational, immoral people (Proverbs 10:19; 17:28; Matthew 7:6; Titus 3:9–11). David's own son, Solomon, would later write about the need for such discernment. Ecclesiastes 3:7 says there is "a time to keep silence, and a time to speak."

Perhaps David felt like Asaph, who had doubts about God's fairness. Asaph suffered but saw evil people experiencing success. Those doubts shook his faith. He said, "But as for me, my feet had almost stumbled, my steps had nearly slipped. For I was envious of the arrogant when I saw the prosperity of the wicked" (Psalm 73:2–3). Later in psalm 73, Asaph remembers the fate of wicked people. In psalm 39, David remembers his own limitations, to soothe his urge to lash out at wicked people.