'O God' in the Bible

For others, of their own accord, tell about the welcome I had from you, and how you turned to God from your idols, to be slaved of a true and living God,

For this reason also I am giving continual thanks to God, because when you heard from me the spoken word of God, you received it not as the word of men, but as the word of God (which in truth it is), who himself is effectually at work in you believe.

For you, brothers, began to follow the example of the churches of God in Judea, which are in Christ Jesus; and you in your turn suffered at the hands of your fellow citizens persecutions like to those which they endured from the Jews??15 The men who killed both the Lord Jesus and the prophets, and drove us out??hey are displeasing to God, and are the enemies of all mankind.

For what thanksgiving can I render again to God in your behalf, in return for all the joy which you cause me in the presence of my God?