'O God' in the Bible

It will be [considered] righteousness for us [that is, right standing with God] if we are careful to observe all this commandment before the Lord our God—just as He has commanded us.

“They sacrificed to demons, not to God,To gods whom they have not known,New gods who came lately,Whom your fathers never feared.

‘See now that I, I am He,And there is no god besides Me;It is I who put to death and I who give life.I have wounded and it is I who heal,And there is no one who can deliver from [the power of] My hand.