Thanksgiving in the Bible is the giving of thanks to God for everything that we receive at his hand. We receive from him our lives and the food and drink to sustain us. Every good thing in our lives comes ultimately from God and we owe him thanks for all.
Acts 17:25... seeing he giveth to all life, and breath, and all things;
Leviticus 7:12 If he offer it for a thanksgiving, then he shall offer with the sacrifice of thanksgiving unleavened cakes mingled with oil, and unleavened wafers anointed with oil, and cakes mingled with oil, of fine flour, fried.
Leviticus 22:29 And when ye will offer a sacrifice of thanksgiving unto the LORD, offer it at your own will.
Psalms 69:30 I will praise the name of God with a song, and will magnify him with thanksgiving.
Psalms 95:2 Let us come before his presence with thanksgiving, and make a joyful noise unto him with psalms.
Psalms 100:4 Enter into his gates with thanksgiving, and into his courts with praise: be thankful unto him, and bless his name.
Psalms 107:1 O give thanks unto the LORD, for he is good: for his mercy endureth for ever.
It was a feature of the life of Daniel.
Daniel 6:10 Now when Daniel knew that the writing was signed, he went into his house; and his windows being open in his chamber toward Jerusalem, he kneeled upon his knees three times a day, and prayed, and gave thanks before his God, as he did aforetime.
It is enjoined upon Christians by Paul to be part of everyday life.
Ephesians 5:20 Giving thanks always for all things unto God and the Father in the name of our Lord Jesus Christ;
Philippians 4:6 Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God.
Colossians 3:17 And whatsoever ye do in word or deed, do all in the name of the Lord Jesus, giving thanks to God and the Father by him.
1 Thessalonians 5:18 In every thing give thanks: for this is the will of God in Christ Jesus concerning you.
Hebrews 13:15 By him therefore let us offer the sacrifice of praise to God continually, that is, the fruit of our lips giving thanks to his name.
We should not eat without first giving thanks.
1 Timothy 4:4 For every creature of God is good, and nothing to be refused, if it be received with thanksgiving:
Paul gave thanks before he ate.
Acts 27:35 And when he had thus spoken, he took bread, and gave thanks to God in presence of them all: and when he had broken it, he began to eat.
Christ gave thanks when he fed the 5000.
Matthew 15:36 And he took the seven loaves and the fishes, and gave thanks, and brake them, and gave to his disciples, and the disciples to the multitude.
It is an important part of the Lord’s supper.
Luke 22:17 And he took the cup, and gave thanks, and said, Take this, and divide it among yourselves:
Luke 22:19 And he took bread, and gave thanks, and brake it, and gave unto them, saying, This is my body which is given for you: this do in remembrance of me.
When we meet to remember Jesus in bread and wine we likewise give thanks.
In the bread and wine remembrance is made that he lay down his life that we might have the hope of eternal life in the kingdom of God.
By belief of the gospel and baptism into Christ we can be saved from sin and death.
Mark 16:16 He that believeth and is baptized shall be saved;
Eternal life through Christ is the ultimate gift of God.
Colossians 1:12 Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light:
I hope this helps.