Why should a person praise God? It is because of "all his benefits.” David lists what he means by God's benefits in verses 3-5. 

1. Forgiveness of sins (v. 3). The first thing David is thankful for is the forgiveness of his sins. Rightly so! For this is the greatest of all gifts that we can receive from God, and the first we need to have.

I want to address a number of questions regarding this psalm, arranging them in such a way that the successive verses of the psalm give the answers. The first question I want to ask is this: How should a person praise God? The answer of this psalm is in verses 1 and 2. It is "with all my inmost being" or with all my soul.

Have you ever asked yourself to whom the psalms are spoken? To whom are they addressed? The first answer that comes to mind is that they are addressed to God, and it is true that some of them, probably most of them, are. But some are spoken to other people—some to the righteous, some to sinners, some to Israel, some to the Gentile nations and other groups. In Psalm 103 the psalmist is speaking to himself.

3. The church of the future. One of the most fascinating things about the transformed, global outlook of the psalmist is that it extends not only outward geographically but also forward into time. Indeed, he sees his own time relating to future time, for he is sure that what God is about to do to save and deliver his people will be recorded in writing to be a source of blessing for the future church: “Let this be written for a future generation, that a people not yet created may praise the LORD” (v. 18).

Yesterday we observed that in verse 12 the psalmist begins to focus on God. But that is not all we can observe at this important turning point in the psalm. For it is not just a case of the writer turning his reflections from himself to God, anchoring himself in God's eternity. Having done that, and thus having broken the damaging preoccupation with self that so often strangles our spiritual lives, the psalmist now finds himself thinking about other situations and other people and praying confidently for them. In them he knows that the work of God will go on.