"For the Word of the Lord is upright, And all His work is done in faithfulness.” (v.4)
Here in Psalm 33 David writes, “Sing for joy”, “Give thanks to the Lord”, “Praise Him with the harp”, “Sing a new song, and give a shout of joy” (vv.1-3). Why? Because "the Word of the LORD is upright, and His work is done in faithfulness” (v.4).
Simply put the psalmist is saying, God's Word is true and He is faithful in all He does. This applies to anything that could happen to us, regardless if it seems good or bad. And, because of His “unfailing love,” which He will never rescind, He will become our strength and our shield to see us through the times of trial (v.20), leaving our hearts to rejoice in Him for trusting in His name (v.21).
The faithfulness of God's Word caused David to sing unto the Lord, should we not do the same? Therefore, it is fitting that God’s people should sing praises to Him for all He has done, and what He is yet to do. And not just in church, but at anytime the Spirit moves you to “Sing" to His great name.
The Truth: "And they sang a new song, saying, “Worthy are You to take the book and to break its seals; for You were slain, and purchased for God with Your blood men from every tribe and tongue and people and nation.” (Revelation 5:9)
Note: Read also Revelation 5:10-14
