Gathered Worship and the Promotion of the Gospel
In Psalm 96, the Psalmist calls on God's people to sing his praises before the nations. The idea seems to be that in the simple act of gathering to worship God each week, unbelievers have an opportunity to overhear the truth of the one true God and become worshippers themselves.
When we gather together to worship God we promote his glory to the world. We sing a new song. A song unlike anything else we hear in our culture - a song of true hope and grace.