'O God' in the Bible

We give thanks to God always concerning all of you, making mention constantly in our prayers,

For [they] themselves report about us, what sort of welcome we had with you, and how you turned to God from idols to serve [the] living and true God,

And because of this we also give thanks to God constantly, that [when you] received God's word {that you heard} from us, you accepted [it] not [as the] word of men, but as [it] truly is, [the] word of God, which also is at work in you who believe.

who killed both the Lord Jesus and the prophets, and who persecuted us, and [who are] not pleasing to God and [are] opposed to all people,

For what thanks can we repay to God concerning you, because of all the joy [with] which we rejoice because of you before our God,

For if we believe that Jesus died and rose [again], thus also God will bring those who have fallen asleep through Jesus together with him.