'O God' in the Bible

Also I shook out my lap, and said, So God shake out every man from his house, and from his labor, that performeth not this promise; even thus be he shaken out, and emptied. And all the assembly said, Amen, and praised Jehovah. And the people did according to this promise.

For they all would have made us afraid, saying, Their hands shall be weakened from the work, that it be not done. But now, O God , strengthen thou my hands.

For in the days of David and Asaph of old there was a chief of the singers, and songs of praise and thanksgiving unto God.