What does Psalm 42:4 mean?

As the psalmist prayed fervently to the Lord, he recalled leading a procession of worshipers to the sanctuary in Jerusalem. This strongly suggests the writer was a worship leader. This corresponds to the "Sons of Korah" mentioned at the beginning of the psalm (Psalm 42:1). They seem to have been a group connected to worship and music, as well as upkeep in the temple (1 Chronicles 9:19–20; 2 Chronicles 20:19). As the multitude moved along, they shouted with joy and sang praises.

Perhaps the festival alluded to in this verse was the Feast of Tabernacles (Leviticus 23:39–43). Although believers of the church age are not under the Law and are not required to observe the Jewish feast days, they should worship the Lord joyfully and praise Him. Colossians 3:16 admonishes believers: "Let the word of Christ dwell in you richly, teaching and admonishing one another in all wisdom, singing psalms and hymn and spiritual songs, with thankfulness in your hearts to God." Just as the psalmist enjoyed going to the sanctuary to worship the Lord, Christians should look forward to attending church, where they fellowship with other believers and worship the Lord.