Thanksgiving Is A Command

A Command in the Psalms (Psalms 75:1, Psalms 107:1; Psalms 118:1; and Psalms 136:1-3)
Psalms 75:1
We thank you, O God!  We give thanks because you are near.  People everywhere tell of your wonderful deeds.
Psalms 107:1
Give thanks to the Lord, for he is good!  His faithful love endures forever.
Psalms 118:1
Give thanks to the Lord, for he is good!  His faithful love endures forever.
Psalms 136:1-3
1  Give thanks to the Lord, for he is good!  His faithful love endures forever.
2  Give thanks to the God of gods.  His faithful love endures forever.
3  Give thanks to the Lord of lords.  His faithful love endures forever

A Command in the Prophets (Isaiah 12:4 and Jeremiah 33:11)
Isaiah 12:4
In that wonderful day you will sing:  “Thank the Lord! Praise his name! Tell the nations what he has done.  Let them know how mighty he is!
Jeremiah 33:11
the sounds of joy and laughter. The joyful voices of bridegrooms and brides will be heard again, along with the joyous songs of people bringing thanksgiving offerings to the Lord. They will sing, ‘Give thanks to the Lord of Heaven’s Armies, for the Lord is good.  His faithful love endures forever!’  For I will restore the prosperity of this land to what it was in the past, says the Lord.

A Command in the New Testament  (Ephesians 5:20; Philippians 4:6; Colossians 3:15, 17 and I Thessalonians 5:18)
Ephesians 5:20
And give thanks for everything to God the Father in the name of our Lord Jesus Christ.
Philippians 4:6
Don’t worry about anything; instead, pray about everything. Tell God what you need, and thank him for all he has done.
Colossians 3:15, 17
15  And let the peace that comes from Christ rule in your hearts. For as members of one body you are called to live in peace. And always be thankful.
17  And whatever you do or say, do it as a representative of the Lord Jesus, giving thanks through him to God the Father.
I Thessalonians 5:18
Be thankful in all circumstances, for this is God’s will for you who belong to Christ Jesus.

The Command to Give Thank Offerings  (Leviticus 7:12-15; 2 Chronicles 29:31 and Psalms 107:22)
Leviticus 7:12-15
12  If you present your peace offering as an expression of thanksgiving, the usual animal sacrifice must be accompanied by various kinds of bread made without yeast—thin cakes mixed with olive oil, wafers spread with oil, and cakes made of choice flour mixed with olive oil.
13  This peace offering of thanksgiving must also be accompanied by loaves of bread made with yeast.
14  One of each kind of bread must be presented as a gift to the Lord. It will then belong to the priest who splatters the blood of the peace offering against the altar.
15  The meat of the peace offering of thanksgiving must be eaten on the same day it is offered. None of it may be saved for the next morning.
2 Chronicles 29:31
 Then Hezekiah declared, “Now that you have consecrated yourselves to the Lord, bring your sacrifices and thanksgiving offerings to the Temple of the Lord.” So the people brought their sacrifices and thanksgiving offerings, and all whose hearts were willing brought burnt offerings, too.
Psalms 107:22
Let them offer sacrifices of thanksgiving and sing joyfully about his glorious acts.