Psalm 95:1-3 — O come, let us sing unto the Lord: let us make a joyful noise to the rock of our salvation. Let us come before his presence with thanksgiving, and make a joyful noise unto him with psalms. For the Lord is a great God, and a great King above all gods.
1 Thessalonians 5:18 — In every thing give thanks: for this is the will of God in Christ Jesus concerning you.

I had an odd question pop into my mind. Why are we told to give thanks? I don’t mean “list all the things for which we should be grateful”. I mean why is the practice of thanksgiving important?
Of course common decency suggests that when someone pours gifts on you, especially when you’ve done nothing to deserve them, thanks are in order. But this is something else …
As I thought about this, the first thing that struck me is that there is a relationship between gratitude and generosity. I know … gratitude isn’t exactly the same as thanksgiving. But thanksgiving calls to mind the things for which we are grateful, and recalling how much we have been given will surely prompt generosity: “For unto whomsoever much is given, of him shall be much required” (Luke 12:48)
It seems to me, too, that when I sincerely express my appreciation, or someone thanks me, it helps to build a relationship — over time even a loving intimacy. Thanksgiving is a way of acknowledging the dependent relationship I have with God.
It’s not just common courtesy though, or even an expression of dependency. Thanksgiving is about building faith.
Sometimes, life can be really tough. No surprise I know. But then we come across verses like 1 Thessalonians 5:18, “In every thing give thanks.” Feel free to inspect that verse from all directions. Forwards, backwards, up or down — it doesn’t matter — you won’t find any wiggle room. There is nothing for which you should not give thanks. David knew this truth. See what he said in his old age when he was faced with Adonijah’s attempt to usurp the kingdom:
O God, be not far from me: O my God, make haste for my help. Let them be confounded and consumed that are adversaries to my soul; let them be covered with reproach and dishonor that seek my hurt. But I will hope continually, and will yet praise thee more and more. (Psalm 71:12-14)
Thanksgiving — in the good times and bad — is a way of affirming the beloved truth: “And we know that all things work together for good to them that love God, to them who are the called according to his purpose.” (Romans 8:28)
I think I could find many other reasons for us to be instructed to give thanks but here are three good ones … It’s only polite, it makes us generous, and it builds our faith. “Let us come before His presence with Thanksgiving.” Indeed. Always.