As already mentioned, the author of Psalm 66 is not given in the title, though David seems rather likely. The perspective in the first part of the song (verses 1-12) is from the plurality of God's people (using the pronouns "us" and "we"), while the latter part (verses 13-20) is from a singular perspective (using "I" and "me").

In the spirit of the previous psalm, the psalmist calls on the whole earth to praise God and acknowledge His awesome works (verses 1-3a) and then, to God, prophetically says that in the future "all the earth shall worship You" and "submit themselves to You" (verses 3b-4).

The psalm calls on all to come and see the great things God has done and is doing for people (verse 5)--to witness and experience it firsthand or to look into what is recorded in Scripture. God delivered Israel from Egypt by parting the Red Sea and making a dry-land passage to freedom (verse 6). God also dried up the Jordan River so that "all Israel crossed over on dry ground, until all the people had crossed completely over the Jordan" (Joshua 3:17). Yet in declaring this message to the world at the time of Christ's return, the wording here could also refer to the parallel crossings over water on dry land that will occur at that time-when "the Lord will utterly destroy the tongue of the Sea of Egypt...[and] shake His fist over the River [Euphrates]...and make men cross over dryshod" (Isaiah 11:15).

God's people are able to declare that He "has preserved our lives and kept our feet from slipping" (verse 9, NIV) even though He has tested them (verse 10). The tests are likened to the refining of silver, to being captured (perhaps imprisoned), to being afflicted on the back (perhaps through the lash or in bearing burdens) and to suffering oppression--in summary, "We went through fire and water, but You brought us out to a place [or state] of abundance" (verse 12, NIV). As God says through Isaiah of His intention to preserve His people: "When you pass through the waters, I will be with you; and through the rivers, they shall not overflow you. When you walk through the fire, you shall not be burned, nor shall the flame scorch you. For I am the Lord your God, the Holy One of Israel, your Savior" (Isaiah 43:2-3).

On the occasions of personal deliverance, the psalmist promises to bring thank offerings (verses 13-15). And he will talk about the wonderful things God "has done for me" (verse 16, NIV). Whereas verse 5 called on all to "come and see" God's works toward humanity, the psalmist now directs those who have been stirred to fear and honor God to "come and hear" his individual witness (verse 16)--what God has done for one, for him, and will also do, it is implied, for each of them.

Then notice the realization of verse 18, which is an implicit warning to others hearing this witness: "If I regard iniquity in my heart, the Lord will not hear me." This is in a present or continuing sense. The NIV renders this verse in the past tense, as expressive of what had occurred in this episode: "If I had cherished sin in my heart, the Lord would not have listened." Either way, we are told here that the harboring of sin, failing to confess it and forsake it, and the nurturing of sinful thoughts will thwart effective prayer. We find this important message in other passages of Scripture as well (see Proverbs 15:29; Proverbs 28:9; Isaiah 1:15; Isaiah 59:1-2).

Conversely, the apostle John tells us: "Beloved, if our heart does not condemn us, we have confidence toward God. And whatever we ask we receive from Him, because we keep His commandments and do those things that are pleasing in His sight" (1 John 3:21-22). Psalm 66 expresses this very confidence, the psalmist stating in verses 19-20 that God on this occasion has certainly listened to his prayer and has not rejected it nor withheld His hesed--His steadfast love and mercy.