'O God' in the Bible

Unceasing thanks are due from us to God on your behalf, brethren. They are appropriate because your faith is growing greatly, and the love of every one of you for all the others goes on increasing.

For these are a plain token of God's righteous judgement, which has in view your being deemed worthy of admission to God's Kingdom, for the sake of which, indeed, you are sufferers.

And from us thanks are always due to God on your behalf--brethren whom the Lord loves--because God from the beginning has chosen you for salvation through the Spirit's sanctifying influence and your belief in the truth.