What does Psalm 35:15 mean?

The former friends who turned against David (Psalm 35:11–14) are celebrating as David has trouble. "Stumbling" in this verse suggests calamity, as in Job 18:12 and Jeremiah 20:10. David also refers to a group of strangers, calling them "wretches," which may also be translated as "those crippled" or "ruffians." The main implication is that of coarse, immoral men. This mob is constantly harassing David, including insults intended to tear him apart (Psalm 35:16). Yet, David did not know why they were behaving in such an evil way. He had done nothing to hurt them. Indeed, he had prayed for them. When he was expelled from Saul's court and branded as a criminal (1 Samuel 19:1–2), these former allies were happy and gleefully persecuted him.

Persecuted believers may identify with David. Although they share the gospel because God's love compels them to do so, they encounter hostility. The apostle Peter tells his readers not to be surprised at the fiery trial when it comes upon them. In that specific context, this might have included the threat of being burned at the stake. He tells them to rejoice if they are insulted for the name of Christ, they are blessed (1 Peter 4:12–14).