I think, in German there are to possibilities:
"In Gottes Namen!"
"Im Namen Gottes..."
The first one is more of an exclamation. A shocked (melodramatic) mother seeing her child covered in dirt might say that.Similar to that is "Um Himmels Willen!" (For heaven's sake!)
The second one is used as a cause... A bishop is doing something in the name of God, for example.