'O God' in the Bible

And it came to pass during those many days, that the king of Egypt died. And the children of Israel sighed because of the bondage, and cried; and their cry came up to God because of the bondage;

And Moses said to God, Who am I, that I should go unto Pharaoh, and that I should bring forth the children of Israel out of Egypt?

And Moses said to God, Behold, when I come unto the children of Israel, and shall say unto them, The God of your fathers hath sent me unto you; and they shall say, What is his name? what shall I say unto them?

And Moses went up to God, and Jehovah called to him out of the mountain, saying, Thus shalt thou say to the house of Jacob, and tell the children of Israel: