Thanksgiving is an inward offering—something that may or may not be expressed publicly—that first appears in the New Testament. There are three characteristics of thanksgiving that deepen our understanding of its purpose. First, thanksgiving is an expression of the fullness of the Holy Spirit. The apostle Paul instructs us in Ephesians 5:19-20 that the natural overflow of the Spirit is to encourage one another with psalms, hymns, and spiritual songs, to sing and make melody in our hearts, and to perpetually give thanks.
Here’s the second characteristic: Thanksgiving cultivates faith. Therefore, it must permeate all that we do, especially our praying. We should soak our prayers in thanks, never asking God for something without first gratefully recalling what He has already done. Thanksgiving for God’s past faithfulness overcomes inertia in our present faith; it gets the wheels moving in our spirits, like a starter on the engine of faith.
This leads us to the third truth: Thanksgiving triggers faith for miracles. In musical terms, we might call it a prelude to the faith march. Remember, even though Jesus was the Son of God, He nonetheless ministered strictly as a Spirit-filled man, just like you and me. It was the Holy Spirit working through Jesus Who performed this miracle, and it was thanksgiving on Jesus’ part that invoked the Spirit’s power. Thanksgiving, therefore, triggers faith for the miracle-working power of God.
From: The Power of Praise and Worship by Terry Law