The main focus of this psalm is God’s covenant love for his people. It begins with the David’s personal praise of God, but having thought of various divine blessings the psalmist closes with a call for universal praise. So great are the things God does for his people in salvation that it is only right that he is praised by the highest creatures (the angels) and all possible lower creatures as well as by the psalmist (vv. 20-22).
In verse 1, David calls upon every part of his personality to praise the Lord. When he refers to God’s name he has in mind God’s character. Clearly David understands that the Lord is a gracious God who has freely given many benefits (v. 2).
In verses 3-5 David mentions several personal blessings he has received from the Lord. He has been (1) forgiven, (2) healed from a deadly disease (which may be a figurative description of sin or, in David’s case, a recovery from a serious illness that threatened his life), provided with (3) abundant mercies (the idea behind the word translated ‘crowned’ is ‘surrounded’) and (4) rejuvenated (given great satisfaction). God provides these blessings freely.
In verses 6-19, David speaks of the nation of Israel rather than only himself (we can see the change from ‘your’ in verses 1-5, by which he was speaking to himself, to ‘our’ and ‘us’ in verses 6-19). What was true of him as an individual is also true of his people as a whole. He mentions several ways in which God was good to Israel: caring for the oppressed (v. 6), revealing his laws (v. 7), merciful, patient and kind (v. 8), forgiving (vv. 9-12), compassionate (v. 13) and considerate (v. 14).
David realises that the Lord is completely different from humans. They are finite whereas the Lord is eternal (vv. 14-17). It is impossible for them to work in the future but the Lord will love his people in every generation. Because he honours his covenant, he will bring spiritual blessings into the families of those who live by his requirements (vv. 17-18). He can do all this because he is he sovereign God in complete control (v. 19).
What he did for Israel the Lord continues to do for his church. So there are many reasons why we should praise him.