By referring to the great God,
Tattenai is not claiming to be someone who knows and worships the Lord. He was most likely also a polytheist like the rest of the Persian people. They believed in the existence of many gods. He uses the term great God
because that is most likely his summary of what the Jews have told him. Their God, the God of Israel, is the great God.
8 Be it known to the king that we went to the province of Judah, to the house of the great God. It is being built with huge stones, and timber is laid in the walls. This work goes on diligently and prospers in their hands.