What does Psalm 149:6 mean?

In this context, the word "their" refers to the people of Old Testament Israel (Psalm 149:2, 4). As with many other psalms, the Israelites are called to worship God with their own voices (Psalm 5:11; 30:4; 98:1). This is an expected re-sponse after everything the Lord has done for them (Psalm 147:13–20). Christians today ought to have the same natural response to God's goodness (Psalm 103:1–2; 2 Corinthians 9:15).

The second command re-lates to Israel's instructions after the exodus (Exodus 12:41). God ordered Israel to conquer the Promised Land, part-ly as judgment on depravedly evil Canaanite culture (Deuteronomy 7:1–5; 9:4–5). This destruction was target-ed at a specific people, for a specific reason (Psalm 149:7), and was to come through ancient Israel alone. The psalmist is not calling on all believers in God, for all time, to wage holy war (Romans 12:19). In fact, this song would have been written after the time of David, as it uses the term "Zion" (Psalm 149:2; 2 Samuel 5:7). By then, there was virtually no chance for Israel to properly complete those instructions. Such encouragements are probably more in reference to the end times victory of Messiah (Psalm 45:3–6) than to an impending campaign.