Thankfulness, or gratitude, is the appropriate response to what God has done—and is still doing—for us. It is something that we owe to God, something we need to pay. But the expression of our appreciation also does something in our own spirits that nothing else can do.
I express it in this way: Thankfulness releases our spirits for acceptable worship and service. That is why the writer of Hebrews said, “Let us show gratitude, by which we may offer to God an acceptable service with reverence and awe” (Hebrews 12:28 nasb). Without gratitude, our services to God will not be acceptable. It is that “attitude of gratitude” that makes our services acceptable and releases our spirits. An unthankful person is bound up in himself. He is self-centered. He really cannot know true liberation. But thankfulness releases our spirits.
In everything give thanks; for this [giving thanks] is God’s will for you in Christ Jesus. Do not quench the Spirit. (1 Thessalonians 5:18–19 nasb)
That is a clear commandment: if we do not give thanks, we are being disobedient. We are also out of the will of God. In addition, failing to give thanks quenches the Spirit. The only release for the Spirit—to serve God acceptably—is through thanksgiving.
Then, notice the warning that concludes Hebrews 12: “For our God is a consuming fire” (verse 29). The writer was telling us, “We have to approach this holy, awe-inspiring God with the right attitude—with humble, thankful hearts.”