The Talmud counts carefully. King David composed one hundred and three psalms, and only after the hundred and third did he allow himself to utter the word Hallelujah. What made him hold back so long?
The answer comes in the verse where the word finally appears. "Let sinners be consumed out of the earth, and let the wicked be no more. Bless the Lord, O my soul, Hallelujah" (Psalms 104:35). David did not let his lips shape that full cry of praise until he had seen, in prophetic vision, the end of wickedness itself. Praise, in his mouth, was not a decoration. It was a judgment on the history of evil.
A listener may notice that the running total should be one hundred and four, not one hundred and three. The sages explain the missing psalm by pointing out that Psalm 1, "Blessed is the man," and Psalm 2, "Why do the nations rage," are counted as a single psalm. They form one continuous thought, and the tradition numbers them as one (Berachot 9b).
The lesson the sages draw from David's restraint is simple. A person may praise God often, but the fullest Hallelujah waits for the moment when the victory of goodness comes into view.