'O God' in the Bible

And they were helped against them, so that the Hagarites, and those with them, were given into their power. For they sent up prayers to God in the fight, and he gave ear to them, because they put their faith in him.

And David went for directions to God; and God said to him, You are not to go up after them; but, turning away from them, come face to face with them opposite the spice-trees.

And say, Be our saviour, O God of our salvation, and let us come back, and give us salvation from the nations, so that we may give honour to your holy name and have glory in your praise.

And this was only a small thing to you, O God; but your words have even been about the far-off future of your servant's family, looking on me as on one of high position, O Lord God.

Then David said to God, Great has been my sin in doing this; but now, be pleased to take away the sin of your servant, for I have done very foolishly.

And David said to God, Was it not I who gave the order for the people to be numbered? It is I who have done the sin and the great wrong; but these are only sheep; what have they done? let your hand, O Lord God, be lifted up against me and against my family, but not against your people to send disease on them.