What does Psalm 35:28 mean?

Believing the Lord would vindicate him and put his enemies to shame, David resolves to broadcast the Lord's righteousness and to praise Him continually. David does not respond to suffering and persecution with complaint or regret; he anticipates that the Lord will make all things right. Before the matter is settled, David already has it in his mind to tell others how the Lord acted righteously on his behalf, and that he would praise God continually.

The apostle Peter encourages persecuted Hebrew Christians to look beyond their suffering and joyfully anticipate the victorious conclusion. He writes: "in this you rejoice, though now for a little while, if necessary, you have grieved by various trials, so that the tested genuineness of your faith—more precious than gold that perishes though it is tested by fire— may be found to result in praise and glory and honor at the revelation of Jesus Christ" (1 Peter 1:6–7). No wonder Paul exhorts believers to "rejoice always, pray without ceasing, and give thanks in all circumstances" (1 Thessalonians 5:16–18)!