'O God' in the Bible

He shall not make himself unclean for his father, or for his mother, for his brother, or for his sister, when they die; because his separation unto God is upon his head.

During the entire time of his dedication, he is set apart to God.

And Moses cried unto the LORD, saying, Heal her now, O God, I beseech thee.

And they fell upon their faces, and said, O God, the God of the spirits of all flesh, shall one man sin, and wilt thou be wroth with all the congregation?

But the firstborn of a cow or of a sheep or of a goat you shall not redeem; they are holy [and belong to the Lord]. You shall sprinkle their blood on the altar and shall offer up their fat in smoke as an offering by fire, for a sweet and soothing aroma to the Lord.

And Balaam said unto God, Balak the son of Zippor, king of Moab, hath sent unto me, saying,

Again Balak said to Balaam, “Please come. I will take you to another place. Maybe it will be agreeable to God that you can put a curse on them for me there.”